Thanks, that's interesting, I haven't heard this before!May I answer this, speculatively? Black holes compress matter. We don't know what happens to it after it passes the event horizon. What if all that missing matter accreted *somewhere else* to the point where it created a Big Bang, releasing all that energy and physical matter? There are black holes all over the universe. If they get large enough to consume galaxies, maybe that is how the universe ends. And a new one begins. Maybe we repeat this endlessly, in time spans we cannot even imagine.
The only things I will add is that according to Hawking, black holes radiate energy and eventually dissipate. So I am dubious if a black hole would actually get large enough to absorb a galaxy.
Technically, the big bang wasn't the beginning of the universe. It was the point at which it began expanding under the influence of momentum and dark energy. The big bang was preceded by cosmic inflation, and we don't really don't have the physics to understand why this inflationary phase happened or how it originated, though speculations are fun.