Hmm, I've never found myself as part of a "movement" in particular, but the question you've posed is an interesting one and I wanted to give my 2 cents anyway. I'm focusing more on having personal websites, since I don't have experience using Fediverse platforms and the like.
I dont know why, but its near impossible to get people to move off of the old sites
From my interpretation, it seems like you want to push the old web as a replacement for mainstream social media sites. But that's kind of like asking people to replace rice with noodles, they're 2 fundamentally different experiences! As you can imagine, someone who is used to the convenience of twitter will likely not be able to find it in maintaining a personal website. Corrupted Unicorn has basically summed up my thoughts on this.
Let's also not forget that it is a privilege to have a laptop you can use, have access to educational resources, to even be able to learn how to build a website for no reason other than personal enjoyment. You can already see how this circle may exclude, let's say, someone whose only means of accessing the internet is through their phone. Nevermind the fact that it is not an expectation for personal sites to meet accessibility standards or even be mobile compatible! (guilty...)
If you really want to promote the old web as a "cause" to join, I think it's not only important to consider the above but also to detail exactly what the goals of the movement is, lest we fall down the path of
Yesterweb.
Some websites like SundaySites have been inactive since last year.
Just to end off this tangent, I actually think that's a strength of the personal web. There is no urge to actively maintain your site, no audience to entertain, no algorithm to please. To create your website is to do it for your own pleasure, and I imagine that's another thing someone who is used to the socmed game will find hard to adapt to

i would love to hear about other events and such that people know of.
The
32-bit cafe hosts code jams every so often! There is also
the html review, which is more of a formal yearly journal.