Black holes evaporate back into particles via Hawking radiation.

But if there is nothing but black holes, the particles end up falling back in. Take that, Hawking!

Fun idea! But space keeps on expanding. So at some point most mass will be in black holes, but every black hole will be so far from every other black hole that even light will travel forever without ever being able to reach another.

No, eventually all black holes are expected to evaporate, with only particles floating around so spaced out no more black holes will form.

And given that in the beginning there was a Big Bang, we can assume that this is what happens when the black hole becomes large enough.

This paper has a mind-blowing idea, that topological defects like magnetic monopoles, cosmic strings, domain walls actually breed

https://arxiv.org/abs/hep-th/9402115

and far far away more of them are being created and inflating, once you far enough way you are in something that looks like our universe, somewhere out there inflation is stopping and the big bang is happening there.

It's easy in my mind looking at the classical black hole picture and wondering what happens around the singularity to wonder if inflation gets re-started inside a black hole and maybe in that old picture where you can go into a rotating black hole and come out in the "asymptotically flat spacetime" it is a universe made by that mechanism.

Of course I think the classical black hole picture might be "not even wrong" and you might run into more than one firewall (such as the inflation zone) on the way there.