Question

Why/how might someone struggle writing two column proofs?

Answer 1

I am not a fan of two column proofs, so my thinking might be biased. The main reason for the struggle is kids don't often understand the right hand column statements, they write them from a memory bank in the head, but don't understand them. See https://mathwithbaddrawings.com/2013/10/16/two-column-proofs-that-two-column-proofs-are-terrible/