I actually looked this exact thing up a couple weeks ago, so maybe there was a tiny spike in googling D&D google analytics.
Anyhow, a couple things:
1) I don't think this is particularly meaningful because the global situation has been so wacky over the last two years, so it is hard to interpret it in any particular way. But the trend from 2014-2020 is most certainly meaningful - but it doesn't tell us anything that we didn't already know.
2) D&D's popularity will inevitably plateau, and probably dip at some point. But it might plateau and then start going up again, in a similar way that sometimes baseball players reach what seems like their peak level, plateau for a bit, then have another spike.
It may be that D&D has maxed out in the US, and possibly in the UK. But has it maxed out in Europe and the rest of the world? Most certainly not. For instance, I haven't heard of a D&D fad in Nigeria or Chile. Will there be? Maybe, maybe not. I think Hasbro wants to find out, and we'll know more after the movie comes out. I suspect we'll see another spike, and then a rise over the following year or two, then another plateau and then, well, who knows...
One minor note: While a lot of factors combined to make 5E as popular as it is today, I think Stranger Things is significantly more impactful than Critical Role and Matt Colville - to the extent that I don't think they're even worth mentioning in the same sentence. Here i think the video maker is confusing his own experience with larger trends.