Technical skills and MMA background

I have a question for you guys.

My question is: How a today fighter would be so good when they have so limiteded skills in other disciplines?

For exemple, Stipe Miocic is a purple belt in BJJ, NCAA Div.1 wrestler (but not all american champ or something like that) and golden golves in boxing. Anyone would have that achievements after some years of training. Stipe can't compete with a national amateur champion in boxing (in a boxing match) or wrestling (in a wrestling match) or with a black belt BJJ competitor.

However, he is the UFC heavyweight champion and knocked out world class kickboxers like former K1 champion, Alistair Overeem. Knockout, not submission.

You can't say "ok, he is a complete fighter and when opponent is a striker, he use his grappling" because Reem is a striker, Hunt is a striker, world class strikers with achievements at highest level in kickboxing and Stipe knocked them out, not submit them.

Justin Gaethje, a WRESTLER that not use his wrestling anytime was able to knocked out Edson Barboza, a world class striker with black belt in muay thai, TKD, very technical striker.

How a simple black belt BJJ competitor would be better in MMA than Royce or Rickson Gracie? Best BJJ competitors that ever was.

And if you say "ok, but they know just grappling", then how a master like Lee Hasdell with technical skills better than anyone in present MMA, with 7th Dan black belt in Karate & Kickboxing, 2nd Dan black belt in Kudo and black belt in Ju-Jitsu and Submission Arts wrestling, how a fighter like him, master in grappling, striking etc. would be under a fighter like, idk, Dominick Reyes.. a blue belt in BJJ with a MMA level good skills of striking.

I can't explain these thing.

Also, how you define technical skills in MMA? A good fighter with no background would be more technical than a black belt master in multiple disciplines? how??

Edson Barboza has to change his style, his stance, and his strategy when fighting someone who knows how to wrestle. If he tries to fight like it was a Muay Thai match, Gaethje would be able to immediately shoot for a takedown. This possibility makes the entire fight different.

I think it could be equated to good fight IQ, game planning, athleticism and reaction timing.

If you have lets say average skills in all areas, yet you have excellent fight IQ, game planning, athleticism and reaction timing then your average skills are enhanced.

GSP had a very good Karate background (2nd degree black belt), later on blackbelt in BJJ.
Later in his added wrestling, which he had no background in and boxing(Jab, Jab, Jab)

But what made him such an elite fighter was Fight IQ, timing, and game planning. Speed and athleticism lent to those skills.

I don't know if this helps with the explanation, but its the only thing that comes to mind

Resume only tells past all those fighrers grew into world beater.
But yeah skills physical gifts and high fight iq got them there.