I'm not sure who are still under MP's promotion, but it seems that they don't have a good stable of fighters that can fight in world stage like Casimero and I think MP promotions is giving their all to support their fighter here.
Manny Pacquiao is an icon in boxing, his promotion will be popular and these fighters under the MP promotion are given a lot of opportunity to fight in the US and that's a great opportunity for them as US is a big market where boxers usually get bigger pays.
I think some boxers under ALA promotion have joined MP promotions as well.