I believe it is set that way because it creates a logic/power loop, if an omnipotent being (A) creates an other omnipotent being (B), if "A" cant undo/prevent what "B" does "A" in not Omnipotent, and if "A" can undo/prevent what "B" does then "B" is not omnipotent, thus ending with one being omnipotent and the other nigh omnipotent.

Therefore there can only be one omnipotent being, and any omnipotent being that creates another risks losing their omnipotent status to their creation or their creation being demoted to nigh omnipotent.

That or its down to who ever states they wish to contradict the others wishes/will first, effectively accidentally using their omnipotence to remove/downgrade the others.

Though with that logic there will technically be 2 omnipotent beings until the moment one contradicts the other or accidently attempts to undo the others work.

The second part seems to be the most logical, two until there is one. With that though, couldnt you have multiple fully omnipotent beings as long as they dont interfere with one another. Say having seperate spheres of influence per agreement or the like.

Also, with omnipotence being above logic, isnt it technically possible to for multiple omnipotents to exist and act aginst one another while still retaining their omnipotence even though logically they should by all rights lose it?

while you could have multiple omnipotent beings at the same time that choose not to interfere with each other, unfortunately that creates a self imposed limitation upon them thus ironically creates a self imposed nigh omnipotent status

With omnipotence their can be no ifs, buts, or, limitation etc. By imposing that rule they add to their power it changes from "I can do anything I want" to "I can do anything as long as it doesn't interfere with the others work" or "I can do anything as long as everyone agrees"

you could make them all have their own reality or realm for them to do as they wish, preventing them from affecting you, but this still imposes a limitation of "I can do anything WITHIN my own realm" and "except in their realm". this would make you Omnipotent in your realm but nigh omnipotent within all realms thus not true omnipotence

In the end if by some miraculous working both/multiple having omnipotence I foresee it ending in one of two ways, they eventually end up using their omnipotence to erase the others from existence, or use it to remove the others omnipotence either to no powers, or to nigh omnipotence by one not wanting the others to mess with something hey did. ending with a power race of who is the most limited, first to limit the others has no limits, then second limited only by first, third limited by first and second, so on and so forth. still ending in only one omnipotent being

It's not that their cant be more then one omnipotent being, its more of how long their can be multiple before the inevitable event brings it back down to one.

I know it may seem both logical in reason and illogical based upon the power set, but them the breaks. The only way to find the absolute truth is find to beings that have omnipotence, make sure they are both omnipotent and not nigh omnipotent (no idea how) then introduce them and see what happens.