I think his diet was like that of a hippo where he was usually a herbivore but in droughts and food shortage triceratops would eat meat. I don't think triceratops was a carnivore on a usual basis and hippos also have bone crushing jaws and yet they only occasionally eat meat.
i read that thing, & i still don't think it ate meat. i can believe that it's jaws were able to crunch through bone, but who's to say it did? wouldn't it make more sense for it to use those strong jaws to crunch through tree bark? that to me, is more likely than Triceratops eating meat.
sincerely, even when they thought it was a herbivore, people knew it's jaws could crunch through bone. why would it's jaw suddenly become weak when it starts to eat meat? anyway, deers don't have bone crunching jaws, they don't need them to EAT SONGBIRDS. (they are known to do so)
You didn't say they became weak, but you said they were too weak to crunch through bone. However, if they could crunch bark and break branches, it could aswell crush hollow and thin bones. It's not going to bite through thick and solid bones like his own, of course, but when eating meat it's most likely that Triceratops acted like deers, boars, pigs, bovines, and other faculative carnivores, nipping at soft meat or eating extremely small animals like songbirds.