Boxing is so far ahead of MMA that the greatest boxer of our generation and arguably one of the greatests of all time took 10 rounds to beat a 0-0 boxer making his professional debut. Light years ahead.
Good try, but hopelessly wrong. If Floyd knocked Conor out in the first round, you'd say the same, "oh, but Floyd is the best of our generarion and Conor is a 0-0 boxer". That's just lame, lame, lame.
No, I don´t believe Floyd ended Conor's career.
But Mayweather was at the time a 40 years old retired boxer who tooled with the MMA monster of fights for seven rounds, until he decided to box and in three rounds gave your boi the spanking of his life. We will appreciate if you could provide ONE video, ONE gif or something showing that at any point of the fight Floyd was in real danger. None. Cero. Nada. Zilch. Conor connected a good left hand in the first round and another one in the second, and Floyd walked through them like a boss. Don´t fool yourself: Floyd has been all his career a pillow-fisted boxer and I can remember him conceding the first three or four rounds in almost every fight in the last decade.
In any case, boxing is so far ahead that a MMA champ has to go boxing not only to make decent cash but also to be recognized as a world-class fighter. Even in Conor's little mind, his global recognition would come by defeating a great boxer. Floyd never even considered the other way round.
This, of course, is not Conor's fault. Boxing has been a worldwide sport for a century, with national federations, amateur federations, is an olympic sport with world organization, etc etc, while MMA is an activity restricted to a bunch of promotions.