I don't think that the problem is that they want to put it on Steam. It make sense for any devs to want their game on Steam. It's that they are getting paid on Patreon while re-working old content instead of new stuff, while the game is near the finish line. I don't know much game that take a break when they have around 10% left till the end, just to do a remaster of the 90% already done.
The Steam platform is one where you pay for a finished game (or an early access, but you don't pay anything else when the final version drop). That's why most devs will put it on Steam when they have a final version (or by seasons).
Right not, they are using Patreon to get paid while working on adapting the same content everyone already played. I understand why they feel the need to adapt it before putting it on Steam, but they are trying to have it both ways. Either you finish the game normally and adapt it after, or take a "break" from Patreon while you are working on the Steam version.
On the other hand: the fans decide what they are willing to pay for. If the devs are upfront and people don't mind paying a monthly fee to see some rework of old content, I really don't mind. That's not something I would pay for, but I can 100% understand why people have a problem right now.
PS: Using the Patreon platform to get paid is pretty much the definition of devs "here to satisfy fans".