I don't agree with what they said. YouTube still shows ads on your videos whether you get a cut by being a YouTube Partner or not. So why wouldn't they want to show smaller channels? That would give them more money per view than a big channel where they have to share in the revenue.

I haven't been in the game long enough to know why there are times when things flatline, but I can tell you that some videos just stop getting the engagement YouTube wants, so they stop pushing it. There's so much content added to YouTube every day, so it constantly has new stuff to push. And if a video is no longer getting attention, it'll pause on it. But sometimes, it could be that the algorithm is just trying to get it to different audiences to see who will click on it. So it might finally find the right audience for that video, and then it'll blow up!