You can cut the echo, meso crap, that’s just ways to describe physiques (you get a six point rating in each section, 1 you show minimal traits, 6 they are dominant (so as an extreme a skinny weakling with narrow shoulders and no fat could be rated 1 endo, 1 meso, 6 ecto), it’s all completely irrelevant to how genetics actually work and hundreds of years outdated (was connected with measuring skulls to ascertain personality, Mesomorphs are supposedly criminals btw).
In mma you want strength p4p (thanks to weightclasses), power and endurance (and decent flexibility also helps), so having a balanced muscle fibre ratio (There’s actually three types, slow twitch type 1 and fast twitch type 2a and type 2b) is optimal. That gives you strength and endurance capability. We see this in athletes like Jones, GSP and Karelin (in wrestling), although most fighters seem balanced, as do rugby players (as opposed to sprint sports where it’s all fast twitch or endurance sports where it’s all slow twitch).
To be strong and powerful p4p you won’t just need fast twitch fibres though you also need an athletic frame (robust joints and skeletal structure/bone size) and high test production. Broad shoulders are often key (again just look at Jones, gsp and Karelin), although thick frames in general (hunt/Cormier) are advantageous here. Longer limbs helps in the striking but as demonstrated by Tyson’s success (and hunt in mma) this isn’t like rowing or basketball where anyone sub 6’4 is coming in at a massive disadvantage, it’s more about how hard you can hit and how much you can take.
Basically it turns out being built like a Greek god looking mother fucker (Yoel) does result in both insane strength/power and durability, which looking at him does make sense.