A 72" reach is not insane for a welter to jr middle. Floyd wasn't a southpaw, but he was very skilled with his left hand. Fans say so and so won easy, but that's only true when the other guy makes a business decision not to risk getting hit or embarrassed to give him the best chance to win.
Don't forget his very unique upper body. Even when he was at 154 he still had a very slim waist, which meant he could move his upper body into angles that his opponent wont anticipate. This became even more important when he turned older, and began using the ropes as protection (something no boxing coach would EVER tell you to do). You just cannot prep for him, there is no sparring partners with the combination of skills and physical talent like Mayweather.
No, he was terrible at it. Watch the Augustus fight. He needs to stop between punches, and he can’t combine his offence with his defence. When he tries to throw combinations it still looks like he he is potshotting because of his lack of fluidity.
The answer is easy Floivd could run faster backwards than other guys going forwards & he could cling like a leech
The Gatti fight is an anomaly, Gatti was a punching bag with zero movement, he blocked punches with his face and didn’t throw back. Whenever he flinched Floyd would react and jump away. It was only when Gatti was standing there completely still that Floyd had the confidence to throw some combinations. Now look at the Augustus fight, because of his constant movement Floyd is flinching all over the place, hesitant to throw and getting bashed on the inside.
Watch how far he sticks his lead foot out. He rarely ever fought anyone with a reach longer than his and if he did, it wasnt significant and they didnt know how to use it. He had fast hands but his speed is way overblown. He NEVER telegraphed his shots. He wasnt a murderous puncher but he was deadly accurate and he knewnwhen/where to throw his lead hand/check hook whichndiscouraged many opponents and dissuaded them from their plans a lot of times andnforced them to reset. With his lead foot out there he had very good balance and it also acted as a range findernfornhim instead ofna punch. When fighters got intona certain vicinity of his lead foot he was such a master of distance he knew exactly where they were in regards to his punches, it acted as a first line of defencenfor him and when fighters got within that range he would pot shot them with perfectly timed and deadly accurate single shots which forced many fighters to have to reset and abandon their approach. He never fought someome with a noticeable reach advantage on him who knew how to use it for a reason. And by that time hebhad mastered the shoulder roll and had phenomenal head and upper body movement and was very underrated in his ability to parry shots with his gloves and arms as well, that's why it was difficult to put in good work onnhis body. With his stance, style, talent, reach, footwork, timing, accuracy, single shot speed and ability to not telegraph his punches, defense and safety first approach, base, and mastery of the shoulder roll, he effectively made himself a much MUCH smaller target than he was which was compounded by his mastery of the shoulder roll, footwork, and ring IQ. Like Loma, he struggled most with come forward swarmers and brawlers who were at least a little unorthodox. Against guys like that, guys that didnt carebwhat he did and was hell bent on doing what they set out to do, he lost a large element of control. Boxers like Loma and FMJ were/are damn near impossible to beat when they are in their comfort zone and in total control of the fight. There were numerous things both guys were masters of in-fight at a truly elite level -- and many of them were very subtle things -- that manipulated their opponent and funneled them right into that controlled environment the fight was now taking place in. Fighters who are super skilled, like the most elite skilled fighters in boxing -- a lot of times their achillies heel are fighters who are levels below them in skill and talent, have a come forward swarming or even brawling style, and have tremendous physical and mental toughness who remain focused and stick to their plan no matter what and dont let their opponents talent, skill, and gameplan have any affect on them and what they do and dont let allow themselves to be starstruck or even impressed in the slightest by their opponents talent, skill, reputation , or anything affect them at all.
Mayweather was unbelievably skilled though and I always found it so ingenuous how he used his lead foot as a range finder/indicator just like a jab but so much more ingenuous. I'm talking later and heavier Mayweather not the younger and lighter Mayweather. Just goes to show that pretty much if you want to be a true master of the sport and adapt accordingly as you age you have to start off at a very young age because you get such a better understanding of boxing as a whole much better and after competing for that long against world class comp you know the sport inside and out. Even with all the corruption tied to him FMJ was still an absolute master and as skilled as anyone innthe modern era.