I don't think any of them except Shinji thought they could go full time, it's more about keeping people interested in whatever they want to do at home.
Vance worked out his prank calling thing which is fun for him and keeps him in beer long term.
Jimmy, I assume, is going to attempt to auction shit, which will probably go really badly but you can at least follow the logic of why he would want the attention even if it's just from a small handful of people.
Yeah Shinji probably thought that he would get a lot more viewers / engagement. I feel that he got disheartened and so now he's silently quitting, just like he did in the tank. The setup with "Crash" doesn't help much either, if anything he alienated more people having him act as a wingman for his streams.
Tayleigh has been a pleasant surprise. Actively interacting with the audience for the entire stream (paypigs and livechat "plebs" alike), seems to really enjoy it and she tries hard to be entertaining.
She could pass Josie in the future, as she has some talents that are compatible with a wider audience (crochet, guitar) and doesn't exclusively pander to fishtank orbiters. But it's really hard to go to 30k from 5k, and raising your active viewers needs tons of dedication and consistency in the long run.
One Thing ive noticed (someone needs to educate on me this) is how much lower their follower counts are compared to S1. Unless im capping i remember Jon-Josie (possibly Letty) all getting over 10k followers extremely quickly. Most of the S2 fish seem to be at 5K
The main cause of this is the fact that none of the top 3 fish gained exposure or did any extended post-tank collabs / Q&A with Sam and Jet like Letty and Josie did post S1.
Off the top of my head, Tayleigh was on the Alex Stein show for a 30 min segment (which again was nothing special and the audience doesn't really overlap) and Brian was on the freshly set-up Hong Kong podcast with Chris Lynch and Ben (which is sleep inducing and has 3k subs on its own). No other collabs with the main components of the show or anyone directly affiliated as far as I know.
I remember Sam and Jet actively endorsing everyone to support and subscribe to Josie and Letty's channels, in order to get them through the superchat and monetization barrier quick. They also had a 2-week (?) stay in RI, so they got mentoring on how to stream, from people who were arguably a lot more experienced. This can go a long way if you've never done this shit before. Lastly, I can only speculate on how much higher the numbers and current engagement would look like had that happened with Tayleigh for example (who can support her own weight and keeps up with the work).
It is of note here that Letty gave up on streaming after a couple of months of erratic content (which was almost only fishtank related) and even then she had accumulated from the total exposure about 15k+ subs on her YT which is still 3 times more than what the current fish have.
Most people interact with Fishtank from third party sources, like recaps, highlight clips and overviews, and also just because it's affiliated with MDE / Sam, so just a small bit of post-tank support would go a really long way on that regard.