I am sorry the highlighted bit reminds me of a young guy who sat next to me at a bar one morning as I was watching a late season Spurs match. After 5-10 minutes of careful study he declared, "soccer is easy...all you gotta do is be able to kick the ball." A lot of the fighters have wrestling backgrounds that go back to the time they were 9 or 10 and most have trained in some combination of Muay Thai, Jiu-jitsu, Judo, Sambo, etc. You and I may not understand everything that they are doing when they are grappling/ground fighting (it is often difficult to see), but it is a lot more technical than "just scrapping." Even moderately skilled jiu-jitsu students are able to defeat much stronger opponents. Joe Rogan (who has a black belt in Tae Kwon Do & used to teach it) talks about getting easily beaten over and over when he first started learning jiu-jitsu, by much smaller/weaker guys who were better skilled at jiu-jutsu.
Below is 6-7 minute video (with terrible narration) of a 150lb jiu-jitsu practitioner versus a 250lb body builder. The body builder's size and strength don't do him any good when he is confronted by a trained grappler.
Agreed, I think had Mayweather tried MMA then Connor would have quickly taken him down and either submitted him or TKO'd him. I don't think it would have been much of a contest.