First of all, that is a particularly negative view on human nature and those that subscribe to that are not necessarily the proponents of democracy.
Like you seem to hint at Thomas Hobbes and his idea of homo homini lupus est. In which he rejects that humans are social animals drawn to each other for company and cooperation and instead envisions the original "state of nature" by asserting that every human is a solitary predator who considers everything and everybody as fair game.
So his conclusion from that is essentially an early version of the prisoner's dilemma. Where he acknowledges that cooperation would be the ideal solution, but where if you assert selfish players the consequence would be a conflict scenario with the worst possible outcome. And he argues that rationality is insufficient to avoid that as it is rational for the selfish individual to be to put themselves first.
So Hobbes' solution to that problem, of his own creation, is the creation of a powerful state (Leviathan). So if the state of nature leads to constant struggles over power, his solution is to resolve that struggle by giving all of the power to one all powerful entity.
So in that regard I'd disagree with Ted Wrigley's, otherwise very good answer, in that Hobbes actually was arguing in favor of a dictatorship and totalitarianism. His Leviathan is more or less explicitly a tyrant. In fact he MUST be a tyrant in order to fulfill his role. The Leviathan must have (according to Hobbes) have absolute, unrestricted and undivided power over everything. So afaik for Hobbes resistance MUST be futile. So the only resistance allowed is the defense of one's dear life. Like the threat of being crushed becomes less threatening if you're already getting crushed if you don't resist. So unless you go towards the religious and a threat of a bad afterlife, even the power of the Leviathan is limited at that point.
And Hobbes apparently hinted at a preference for an absolute monarchy (not really democratic). Though while the Leviathan is a personification and Hobbes might have looked favorably on a singular person to fill that role (the idea kinda lends itself in that direction). You can also view it as a metaphorical construct and as a personification of the societal contract itself. So think of something like the monopoly of violence. So without a state you could deal out violence as you see fit, but with a state the state might interdict all violence but it's own. And no one is a match for state level violence. So the smart won't start a fight that they cannot win and the dumb will lose it rather quickly.
So Hobbes was an odd combination of pessimism and optimism in that he saw a necessity to crush individual freedom for people to enjoy a peaceful coexistence, but at the same time believed in a benevolent dictator that would not abuse it's power. I mean technically he couldn't "abuse" his power because it's unrestricted so if there are no rules you're not able to break them... But he thought of that was better than the state of nature.
So as a consequence you can attack that from the optimistic angle and argue that humans are social animals, that we do form societies and that mutual aid is maybe even one of our evolutionary assets as societies that cover for each other are more likely to survive a crisis then a lone wolf.
Or you could be even more pessimistic and argue that, if all people are evil wolves trying to jump at each other if they can and if societies magnify the power beyond the sum of it's parts and if you then give that level of power to a single individual, you create a situation that is WORSE than Hobbes state of nature. Sure in the state of nature everyone is your enemy but they are weak, attacking you comes at the risk of taking damage themselves, while a strong state can rip you apart without any risk at all.
So rather than giving up one's power to create the Leviathan people might also argue that they trust no one but themselves with that level of power and as a consequence no singular center of power can establish itself. Meaning the centers of power are limited in power or can be restricted in it and if seen as unfit can also be replaced easier. So rather than be subject to the whims of the ruler, the ruler is reliant on the people for it's power and continued rule and as such is supposed to have an incentive to be benevolent.
So rather than an unchallenged power to prevent the struggle or a mutual cooperation, you can also champion the idea of constructive struggle. Where the ordered struggle for power and the limitation of power lends itself to something that could also be democratic.
So you have essentially 2 avenues by which you can end up with a system that spreads power to ever more people (democracy or in it's extreme anarchism), either by deliberately avoiding power and domination and instead focusing on cooperation or because of the complete opposite and a competition in which you're not willing to allow anybody else that edge over yourself. And you can have various levels of collectivism and individualism, so anything between people being completely isolated and avoiding each other as best as possible and people being really close to each other and taking care of each other as much as possible (as that might lead to collective and thus also individual benefit).
Also you have a practical problem with the Leviathan, in the sense of how such a power would manifest itself. That is at the end of the day every system is a democracy. Sure the monopoly of violence allows the state to assert itself as the power, but people nonetheless need to accept and contribute to it. The application of that principle still relies on people willing to volunteer for that job and they still rely on the rest of society to provide for them. So if no one would volunteer to be cop or soldier the monopoly of violence would cease to exist, same if people stopped working and paying taxes, then the state would run a deficit and rather sooner than later become unable to provide for it's goons upon which the monopoly of violence would be unable to be enforced.
So unless there's technology that makes the power to rule over other people independent of the support/cooperation/tolerance of these people it still in practical terms comes down to whether the majority of people agree with the system. So unless you aim for radical individual isolationism you'll have a society and how ever is in charge of that relies on some level of consent or at least lack of dissent of roughly a majority of the people.
So it's not really a paradox to begin with.