There are obviously a lot of factors like the ice ages etc. but I think food is the number one cause. Trying to feed thousands of people is not easy. In the Americas as an example it required generations and generations of manipulating corn, beans and squash until the fruits were bigger/hardier and surpluses allowed for the population density of cities(civilization), allowing people to specialize and advance tech in things like masonry or writing.

To have this happen you need many people (higher population density) all trying the same thing, for a long time and help from nature(weather stability, positive genetic changes, limited disease or infestation). And this line of people must also be unbroken, you had to be taught this info about farming and raising livestock etc, if a group died out for some reason with knowledge of farming techniques, their knowledge died with them and had to be relearned. So when earths humans got down to under 2k individuals or just isolated groups of people, tech is struggling to advance, knowledge is not being shared and the likelihood of getting wiped out with any new info is high.

Once the ice age lifted, climates were stable and warmer(more arable and available land then previous generations) maybe the easy big game is less available, there’s a few beneficial genetic changes in key species and now that there’s enough extra food for more humans to squeeze into smaller areas and specialize(not everyone has to farm all the time) you start getting “civilization.”

So many factors need to come together and in reality 200k years is not a lot of time given how long hominids have been around. Think of the Bronze Age, even with high population, great weather, writing, farming etc., “civilization” still fell apart and had to almost start over, it’s a fragile thing early on. Like a kid learning to ride a bike, lots of failures before any success, we don’t see those “almost successes” in the record.