From what I understand, they moved less because of demonetization, and more because of the chilling effect it had on free speech. They needed to be super-careful in script writing to make sure they didn't anger the YouTube algorithm.
I'll also mention another darker side of this: Google is almost entirely liberal inside. If a liberal channel is wrongly banned, an army of Googlers quickly rushes to fix it. If a conservative channel is wrongly banned, there's internal snickering. AIs are not neutral, and Google's reflects the biases of the people who keep tweaking it.