what i'm seeing happen is that "scholar social" has been closed to new members for months, so academics are now all joining mastodon social & finding each other thru boosts & hashtags. i think i saw the journo thru a hashtag i'm following (he appears to be on a geo instance)
supposedly some small instances block mast soc but i personally want to be on a very wide one & certainly not just siloed w academics esp ones in my closest fields (i like them, but can discover their work w/o serendipity, & feel like not joining the scholar one is good for me)
Good luck, I’ve never found a good broad one and abandoned the fediverse after a year or so. It seems to be good for subreddit type strong interest groups. Not broad.
Some sort of Schelling sorting effect seems to overwhelm the preferential attachment growth of the largest instances. There is inevitably a “founding theme” implied by the founder even if there’s no declared theme