I was reading about the Sturmabteilung & Ernst Rohm's role in the rise of Hitler to power, and subsequent liquidation in the Night Of The Long Knives by the SS. In fact, the attitude of Nazis to homosexuality and prostitution over time give a fascinating insight.
So, defining fascism. The bundle of sticks with an axe is not firewood. It refers to the origins of Doric columns from wood. Admittedly this is speculative, but compelling, given the ubiquity of grooves in early columns. The fascia holds up something greater than individual logs could, a temple, the Parthenon, etc. It was also squarely based on post-democratic Imperial Rome, who's standards of living are thought to have been unmatched from the fall of the Western Empire by any city until London in the 1720 - and specifically, a millennium and a half without the great construction and infrastructure projects that went with that, the 'glories of Rome'.
There were some good things about living in the Roman Empire. The Pax Romana was preferable for many to constant warfare. But what looks justified opposition to oppression, like of Jews or Myceni led to their almost obliteration. And the Germanic tribes eventually sacked Rome, in response to that inability to give ground or reform enough to bring voluntary participation. The power of the senate decreased over time, exactly as capable uncorrupt deputies were most needed to bring about that reform.
Imperial China under the Yellow Emperor was very much a fascist state, but the Qin state ended very shortly after his reign. The bloody Five- and especially Three-Kingdoms periods seem to point to why 'may you live in interesting times' is a curse in China (the war that reunited China after the Three Kingdoms is thought to have killed more than WW1, & when global population was far smaller). The White Lotus & Boxer Rebellions, as well as Genghis Khan's invasion were driven my climatic conditions, flooding and famine, or prolonged winters. The relative resilience of Chinese politics and culture to these perturbations compared to the Romans, seems to be because of their civil service, which allowed some amount of choice of administrators by intelligence, and preserved a large body of written culture. I would directly relate the origins and success of that to Liu Bang and the founding of the Han dynasty who pursued soft-power, rather than the violent, autocratic & short-lived previous Qin state, which first militarily united China, and unified it's written system.
I would apply two arguments to why fascist states tend to instability, which requires violence, despite what appear relative success of Ancient Rome & China.
First is from game-theory, because of the free-rider problem. An individual or group shielded from selection pressure, will tend to become or select for people who don't make good decisions. Hitler made terrible decisions about the retreat from Russia that he should have left to his generals. Although not formally fascist Muammar Gaddafi is another example of unrestricted power/decision making leading to instability. I would argue that many of the Greek myths about kings are warnings about unrestricted power, like Sisyphus & Midus. The shift of chimpanzees from one substantially more powerful male like gorillas, to a leader needing a clique to be able to rule, seems to have been essential to the greater intelligence of chimpanzees, and the track that led to human intelligence - cooperation, reciprocity, and limits on individual power.
Second is from 'The Great Game', the conflict of Russia & the UK over trade routes and influence, recapitulated in the Cold War. Over time the state with less trade routes, less soft power, and less innovation, could not compete. In WW2 it was the cavity magnetron and radar, cracking the Enigma Code, and nuclear weapons (Germany only got as far as heavy water at Telemark). In the Cold War it was the ability of the West to outspend the USSR, on soft power, and the space program, and space-based weapons.
Fascism prioritises the group & it's achievements over the wellbeing of large fractions of individuals. While in some cases these align, for a time, I would argue it is inevitable they will come into conflict, leading to collapse or stasis, and be superceded by better modes of voluntarily cooperative organisation m