Because Hodor has limited mental faculties, it facilitated Bran being able to warg into Hodor when they were getting attacked by... Night's Watch? or wights? I forget.

But yeah, that's another factor that adds to the uniqueness of Bran affecting the past...

Which then begs the question: if Bran warg'ed into Wylis through his vision, does that mean he's even more powerful than before? It's reasonable to assume, given some tutelage under the 3ER, but does that mean he can also warg into people of "average" intelligence (this is assuming present-Bran is not able to warg into present-Hodor if his consciousness is in the past)?

I'm pretty sure I'm overthinking it, but either way I don't think I want to know the answer to that question.