Can a human?

(Evidently not, since humans hadn't managed to do it even with the entirety of human knowledge available to them.)

They used an agent swarm. Could humanity? Of course; it was close to being solved. It might have taken five years

The question you asked was whether the AIs could prove the thing "in a vacuum", without making any use of previous human work. "Close to being solved" is a statement about all the previous human work that mathematicians might have used to do it in five years.

Replication of the development of mathematics by human civilization is a task for an artificial hyperintelligence.

What will anyone do? What will anyone feel their purpose would be? Can't all have the same one, either.

What will the planet 'need' homo sapiens for (arguably it never needed homo sapiens at all)?

Would anyone's time or life really have significant value?

I didn't mean that as "we need hyper-intelligence." I mean that going all the way from nothing to singular, dual, plural grammatical numbers attached to particular nouns to abstract one, two, three, many to zero, one, two, three... to rationals to... is a very long way.