Again, WMMA or not - which anyone subjected to my drunken internet rantings will attest, I'm not a fan of - Rousey and Bethe were both undefeated fighters and they were fighting for a title. Conor and Cowboy are just two guys coming off consecutive losses fighting for nothing.
And while we will never find out, I can almost guarantee that Rousey-Bethe got more PPV buys than Conor-Cowboy will (and if you think that's far-fetched, you don't understand what the ESPN deal has done to the PPV market).
Objectively, Rousey-Bethe was a more meaningful fight and also probably more worthy of headlining a PPV if we are talking pure business (but we can't know that, so it serves neither argument.).
Being undefeated in that era of WMMA does not carry the same merit as you posit, in my opinion. You indicated that there’s more meaning “objectively” which I will ironically object to.
I have been vocal on here in my criticisms of McGregor since the Floyd fight; I even made a post explaining why the UFC might want to think of being out of the McGregor business, but do you sincerely believe that a belt being on the line makes one obviously inferior fight skill-wise more important? McGregor may not be the GOAT he aspired to being, and Cowboy has lost a lot of big fights, but in terms of skill vs skill this is a very high level fight. If you’re saying that Bethe vs Rousey was a better fight, we must simply have different ideas as to what a good fight is.
With the state of MMA’s meritocracy being what it is, I think it’s best to judge fights on purely skill vs skill, and if you do that there have been quite a few PPV main events that don’t match up to this one. I think nothing short of mental gymnastics can convince someone otherwise. If you’re looking for a belt, I get it, but Nicco Montano was a champ and you can’t tell me that literally any matchup for her would be more interesting than Conor vs Cowboy.