That kid can get knocked around by pro Muay Thai kicks but falls from a little tap by Mayweather. Hmmm....
I can't tell you it's not a work, but I can tell you it doesn't make any difference whether it was arranged or not since the kid had 0% chance of winning and 100% chance of losing by KO under boxing rules against Floyd.
Precision, timing, and angles make a difference in the efficacy of a strike. In Muay Thai there are a lot of offensive options, but you also stay at a different distance and with a more squared off stance than in boxing. Up close you have to watch out for elbows, knees, and takedowns from the clinch, and you have to stay squared at range or your lead leg will get destroyed right away.
Muay Thai kicks generate a lot more energy than punches but think about how they're typically landing in a MT fight against someone in a MT fighting stance:
See above where it looks like Buakaw is landing an obscene head kick on some unfortunate fellow. It's hard to tell whether a good Thai kick is going low or high on reaction, so he has his front leg up to defend against a leg kick, and still keeps his hands up and his chin down to defend high, which is correct. In MT kicks are the main thing you're concerned about defending against at range, and they're usually at least partially defended against at any given time.
MT fighters often have not-great boxing because the distances under MT rules trend engagements toward either kicking range or clinch range (elbows, knees, takedowns). Under boxing rules, all of those techniques, including clinching, are illegal, and obviously all offense and defense (other than defensive clinching) revolves around the punch. A standard MT fighting stance also doesn't generate as much punching power for your dominant hand as a boxing stance, which keeps your weak side in front and leads with jabs, with more rotation on pivoting for power punches.
MMA's different too since you have ranged takedowns to contend with and the gloves are a lot smaller. This makes kicking riskier and punches harder to block, among many other things. That's a different subject, but generally MMA striking requires more boxing proficiency, rewarding good boxing and punishing any mistakes direly.
PBF lives and breathes Queensbury rules. His reactions and body movement are honed to razor sharpness for staying in the pocket with someone, taking no damage from their hands and landing clean hits with his hands. It doesn't matter how many hard MT kicks the other guy has walked through. He's not walking through perfectly timed punches to his chin and his technique and reflexes aren't honed for fighting under boxing rules.
I mentioned Giorgio Petrosyan as a far more interesting matchup above (under some sort of hybrid rules...) because he's a technical kickboxer known for his defense, reaction, timing, and good hands. Still, look how differently a high level K-1 fight plays out. Note the distances, the stances, the rhythm, the types of openings that get exploited. It's all very different.