You made a wild guess about the cause. Your defense is that we should ask about the cause. This is a non sequitur, as those are two completely different things.
It's called a discussion and definitely not a non sequitur.
"I wonder if it was because of the recent rules changes made by YouTube", "Wouldn't be surprised if it was because of the recent rule changes YouTube made" and "Do you think this was because of the recent rule changes YouTube made?" are equivalent in what they bring to the discussion. The only difference is you choosing to interpret them differently.
