There has to be a beginning, or there is nothing, if there is no origin of regression, there would be no nothing there now. and now I will tackle “why can’t the universe be uncaused?” Because we wouldn’t be here now, it would stay in that state for ever, am I wrong? Please answer.
1/2 + 1/4 + ... + 1/2^n consider this infinite geometric series, you can proceed on the real line like an ant starting from origin 0 with each step becoming smaller and smaller, you can go on to infinity. But we all know from math this series is convergent to 1, so it has a finite limit=1, and you as the ant is not staying for ever as easily imagined. Now finally, imagine this route from 0 to 1 as a geodesic from north pole to south pole of an ontological finite sphere, and assume that our physical world is nothing but its "stereographic projection", with north pole projected onto the infinitely far place on its projected plane. So this ant's "reflection" on the physical world plane may indeed have infinite regress within this projected physical world, while in the ontology world the real ant has an infinite progress... So intuitively, you may feel exhausted and intellectually absurd to have infinite regress within your world level, however, the same process viewed from a "transcendental" world may be a very well defined finite short process.
Apart from above geometrical model, in philosophy since Aristotle's famous "principle of sufficient reason" within determinism, it's actually necessary to have an infinite regress of cause-effect chain within our physical world. So this philosophical "axiom" so far is consistent with above mathematical possibility, and inspired one of two factions of epistemology called Infinitism. The other school of thought is called Foundationalism, which is more intellectually ambitious and denies its physical possibility.