Not "universes" like the laymen would think of them. It isn't that an entire universe collapsed.
Basically the theory as it currently stands is that there may not have been a big bang persei, and really it's that all space and time will, by default, be expanding in a way similar to just after the big-bang. When that happens there can be local areas that stop expanding due to random fluxuation of the inflation field, and that can give rise to energy differentials that then give rise to matter as we know it.
What this is saying is that there can be little bubbles during that stop expanding, and instead of forming into a universe as we know it, it forms a very low mass black hole. And since these are happening all over the fabric of space time during expansion, when a real universe gets enough of a push to form, it would be littered with these tiny black holes.
However, I wouldn't hang my hat on this. It's going to have to be tested and black holes of almost all sizes have already been ruled out as candidates for dark matter, so it would be suspiciously convenient if dark matter turned out to be in the specific range we haven't been able to look at yet. But it might still be, which is why we still have to look. It'll just need to be confirmed by several groups before it's accepted.