He is skating on thin ice, though, I think. Technically, what he is doing could be called spam, as he is indescriminately following large numbers of people in the hope they will follow him back. That's not using the following function for its intended use, which is to follow people you are interesting in reading. It's quite possible his bahaviour could get spotted eventually and his account could get suspended. The Medium rules do state that they don't want people doing "bulk or indiscriminate interactions, such as following of other accounts (follow spam)".

But then David Perlmutter hasn't had his account suspended yet, even though he's clearly a highlight spammer and has even been reported. I suppose they review each case on its own merits and make a judgment about whether they think the member mostly contributes positively to Medium or whether they are genuinely a nuisance to everyone.

When I was dedicating all my work time to Medium, I did that because I wanted to know for sure whether it was really worthwhile. I felt like I wanted to give it 100% for a bit. But at the time I didn't have much else going on, and I was on benefits, so I felt like I could do that for a bit. But it was only for a few months. Then I realised I needed to find other work on Upwork. And then from last summer I went really hard on the whole Upwork thing, which eventually did pay off. I definitely wouldn't have quit a full-time job to write 100% for Medium before I knew whether it was worth it. That would be foolish.