My favorite idea is that the universe expands because mass-energy in our 4d parent universe is falling into our universe, which is a black hole. We exist as information upon the 4d hole’s 3d event horizon, and experience its inflation as our time dimension (as well as space inflation).

Inflation is accelerating because as the black hole grows it eats more.

Don’t know how crackpot this is. From what I’ve read it actually can be coaxed into fitting observation but there’s just no possible way to test it.