A.H.
I found for my daughter it was because she couldn't communicate what she felt/wanted. I worked on her vocab, taught her what to say if she needed help with something, and focused on expressing feelings. It's amazing to see an almost 2 yo say Mama I'm frustrated. But it stopped her biting. And she has an even bigger vocab now at 5.
Good luck, you'll find what works for your family.
A. H