Sounds like their coach is better at player development. Or there was some
trickery. Who knows? How would you ever prove it?
It is what it is.
On my 1st little league tryout, I batted with my hands reversed. It was because I had never played before, at all. I was also afraid of getting hit by the pitch and stepped out on every pitch.
The coach that picked me had me bat left handed. Thus my hands were not switched and I could see the pitch from right handers better and stopped stepping out. Instant improvement. I eventually became a switch hitter.
So - that can happen. But 5 players sounds suspicious unless most of those good players were coach sons and thus automatically on the team.
You seem pretty competitive to coach in a non-competitive league - as does the other guy.
Now you have been schooled. Get a couple of ringers next season.