It is not crazy, if you take into account that the genocidal war is very popular among Russians, and the only complain they have is that it is not going according to their expectations. They blame the top military officials for that and think that wagner will be more efficient in killing Ukrainians.
Not everyone is on top of who's part of the mercenary company and some people could just see this as "a change", so they would offer some support.
Not making a statement of "how things really are" here, just saying that sometimes an explanation might be "jeez, finally there's some change, maybe something will happen out of this" and not "let me go support these genocidal mercenaries".
He knows the regime is weak and pulled all the levers he could to make it look weaker and get himself more support. He's not tricking anyone, others know what he is but by suddenly speaking against the war he's signalled clearly they have the same immediate goals. I'd imagine that also went through some conscripted or otherwise unenthusiastic soldiers heads when they decided not to confront his mercenaries.
I think Putin expected Russian soldiers to resist when he gave a tough speech last night. They all watched except the air force.