In Rumble World why did my Kyogre mega evolve at the start of the battle?

Question

I thought you have to push that button to mega evolve am I wrong or Kyogre got naughty?

Answer 1

Because it is not Mega-Evolution with Kyogre, it is Primal Reversion

If your Kyogre is holding a Blue Orb, it will Primal Revert (?) at the start of battle. You don't have an option with Primal Reversions.