I would think that the majority of bank accounts, when held by a person who has an estate plan or testamentary documents, goes to direct beneficiaries rather than probate.

It just depends on how the account owner assigned responsibilities and beneficiaries.

You say grandma put Evil Aunt in charge of everything, but not whether formal, legal authorization existed.

A Power of Attorney expires on death, so even if she was formally authorized to wield power, that's not relevant to the estate.