In each of the instances I'd listed above, a reason emerged. Sometimes it was pull, but quite often (Usenet -> Web forums, Digg -> Reddit, MySpace -> Facebook), push played a major component: the extant option was increasingly less appealing to users (or providers, see my "Why Usenet Died" analysis for my take on some of the factors: <https://old.reddit.com/r/dredmorbius/comments/3c3xyu/why_use...>).

The compelling reasons presently are being provided by Twitter and its present owner, Elon Musk. Nothing's changed in Mastodon's offerings over the past several weeks, but much has changed regarding its attractiveness. Social networks are notoriously tippy, and what matters far more than specific featuresets of either the origin or destination systems. If major users transition, many others will follow. If and when that does occur, this can happen with stunning swiftness.

UI/UX are not at present a blocking feature, though as we've both noted, opportunities for improvement exist.

I've seen instances with > 3x increase in traffic as noted in this thread:

<https://freeradical.zone/@tek/109309036456312761>

That's based on available evidence, not hypothetical arguments.