I told all my friends before this fight that the biggest problem McGregor was going to have in this fight would be pacing himself appropriately for 12 rounds. It doesn't matter that he's gone 25 minutes before, the 12 round 3 minute pace is a much different pace. We've seen amazing wrestlers flame out in MMA because they can't adjust to the pace even though they're in phenomenal shape. This is something I know from my own experience in competition and having had to deal with injuries since very early on in martial arts. Someone with inferior cardio can look way more fresh late in the fight if they pace themselves the right way and use experience and veterancy to limit energy expenditure and their opponent doesn't.
Mayweather's gameplan was clear: they thought Conor would be at his most dangerous early on when he can use his youth and athleticism and in any kind of scramble or positioning transition where he can use his footwork and weird angles and unorthodox technique to max advantage.
Mayweather staying flat and letting Conor dance around while staying where Mayweather wants to be, and letting McGregor tire himself out was the gameplan. Not Floyd carrying him. He played it super cautious as he always does, minimized his risk completely, and then once his opponent played into his trap he exploited him completely. A brilliant performance by Mayweather, he understands the game theory optimal approach to boxing better than anyone.