Because so far, all civilisations destroy themselves eventually. Human history is basically a story of civilisations forming, being stable for a short time, and collapsing. The Babylonians, the Romans, the Mongols, the Ottomans. They all fell.
The entities that collapsed would be more accurately described as states/dynasties, not civilisations. These were not human settlements that just vanished. Some fell to external pressures, or at least had their stresses exacerbated by them.
They all fell. But when they fell it wasn’t the end of humanity, because they were just local collapses.
It wasn't the end of humanity because they were replaced by their human local competitors/internal revolts. The collapse of Rome may have been followed by a sustained economic regression in the region but I don't think the same can be said of the others.
For any civilisation/state there are only two possible outcomes
(Excluding the few states/civilisations that went about creating the current system)
There were states/civilisations that collapsed on contact with the globalist system which could be classified under 1 or 2(you could also classify integration as collapse).
tl;dr The assertion that 'all civilisations eventually destroy themselves' is very loadbearing and I think needs quite a bit more support, because
Not a factor IMO imo any more than other factors requiring visuospatial intelligence; cause IMO that's what's inherited not math chops specifically.