Wouldn't other animals with strong bites be capable of crushing bones to eat the marrow inside? The theory is big on assumptions, but I guess that's how it goes when you're trying to figure out what happened millions of years ago.
Because they have no or smaller cheeks. But they have very acid stomachs.
The Comparative Anatomy of Eating
http://www.vegsource.com/news/2009/11/the-comparative-anatom...
Omnivore or Herbivore?
https://livinontheveg.com/omnivore-or-herbivore/
Milton Mills, MD: Are Humans Designed to Eat Meat?
In other words, breaking bones is the easy part; sucking out the marrow is the tricky bit.
https://blogs.scientificamerican.com/laelaps/inside-the-brai...