Anything that performs a genuinely useful social thing with members of the local community can play a role in spreading local class consciousness. Here in the UK back in the day these were working men's clubs, which were both drinking venues and connected to various local sports activities.

The fightclubs that the fascists are constructing are modernising the format of working men's clubs (I guarantee they're 100% male) and embedding themselves in the local community. The role that these working men's clubs can play in a community hasn't changed, just the aesthetics of them hasn't ever updated so they've declined. In particular it's not really obvious why you should join one, whereas it is pretty obvious why you would join a gym for self improvement.

Some of them are chuddy merch grifts specifically intended for fundraising. Now, you could argue that printing shirts and stickers and posters and flags in a co-op is something leftists have done forver, and you'd be right about that, but when you start a store for thin blue line merch or an agitprop site selling reprints of public domain theory or a food supplement grift or whatever these bozos are doing, it makes a difference when you have the funding to start out with several full-time employees, can afford advertising to make yourself known, can data mine information on potential donors and get additional funds if it takes longer to get everything going. It's much easier to scale this kind of stuff up when you go in with more capital than a used screen printer.