If all the tech that the orks have come from the waarh witch is basically "if enough orks believe in something it becomes real" how are they not the dominating faction since all they have to do in order to win is just Believe!
Sadly orks got issues with who leads them, hence many rise up to lead and they got that tribe like thing going on for them.
Because they don't know that it happens. If the orks were more intelligent then they would be unstoppable... but they aren't.
It's not that simple. A rock will never become a Big Shoota, no matter how much the Boys believe in that. What can happen is that the Waaagh! power field allows weapons which would jam after every second or explode in the Orks face to work just fine. It's more like "the special something" rather than the weapon itself.
The Orks aren't aware of the psychic field they generate, and believe their tech works because it's properly made. It also used to be canon if you gave a Ork a sandwich and convinced him it was a gun somehow, he could make it shoot bullets. They later changed their psychic field from it can do anything, to make it do very improbable things. I read an example where if an Ork believes he filled his Wartrukk with gas before he left, but in actuality it has a few drops left, those drops will work the equivalent of a gallon because the Ork believes he has sufficient gas.
Orks have the numbers to take over the entire galaxy. They just hate each other too much to actually get along and stomp everyone. Even a good WAAAGH! has a few bosses who think they're better than the current warboss and fly somewhere else.
