The main thing for me is that Shannon Terry, the guy who founded both Rivals and 247, is doing On3. It seems like he literally takes a few years to build the most successful recruiting/college team site network, makes money, leaves, waits for his non-compete clause to expire, and then starts another one that knocks his previous work down a peg or two--rinse and repeat. Rivals was easily the top dog for a long time after clearly besting Scout and all the other sites that had done recruiting coverage in the early internet era. 247 absolutely ass blasts Rivals now. I have no reason to think On3 won't be a good product given his history.
So there's that. But it's supplemented by the fact that you generally only have two of these sites really going at once. It used to be Rivals and Scout. 247 came along and ended that; it actually absorbed Scout. I can't quite tell who they are or why they care, but there are dudes on Husker247 who are still sort of a Scout crew. Regardless, I think 247 is well-established and not going anywhere. However, Rivals strikes me as shaky. You have a few strong sites like HOL, but overall, I think they're getting their lunch eaten by 247. Callahan even talked recently about how Rivals is nationally making cutbacks on its regional coverage. That's a bad sign. So is Mike Farrell.
If football recruiting weren't completely moribund right now, you'd continue to notice what was already plainly apparent during the 2020 class: HOL's recruiting coverage, and thus a lot of their product, suffered big-time by virtue of how bad the national and regional guys there are. There was a stretch leading up to and including December NSD where we were getting basically every bit of news broken on RSS via people reporting what Wiltfong or 247 team site guys were saying (WiscyDicks, Minnesota, and Miami were all valuable ones). Clouse, for instance, still thought Kaden Johnson was coming to DONU right up until the end. That's not saying he's somehow that much worse than Schaefer (although I think Schaefer is a stronger reporter), but 247 had so, so much more network support.
So yeah, you have a strong legacy board in RSS, one of the more noteworthy football writers in Callahan, and the best MBB reporter in Washut. Maybe that's enough to wait out Rivals becoming third-rate. I don't know, though, and I think Callahan trusts his ability to hustle and knows HOL/RSS would be a massively different place if they tried to substitute in someone else. Other than inertia, there's nothing at all about Rivals that is keeping people there.