Manny can actually run fundraising for charities or even donate using his own wealth like what he used to do to help people in the Philippines. He usually uses his own money to help the poor so I don't doubt his purpose this time. I'm sure that he really wants to help a charity but he also wants to pursue his passion at the same time. He can't go to another regular match since he already announced his retirement so he will be doing the charity works the way he will enjoy his passion. It's also exciting to see the boxing champ in the ring again after a long time.
It is possible. Aside from giving in to the request of some of his fans, he also has a way to put more money in his stash and at the same time gather funds for some charities.
Even though I believe Manny is a kind-hearted charity oriented person, I cannot remove the possibility that he accepted the fight for monetary purposes. Besides, the exhibition fight doesn't have to put anyone at risk since they can always put anything on the contract including not hurting each other but just to showcase their fighting skills and technique.
He's not in politics anymore so I don't think there's a political agenda behind this exhibition match. He might only want to do the sport that he used to enjoy before and as for me, he should still grab the chance as long as he still has strong stamina to enjoy boxing.
Who knows, probably he will run again on the next election if not a president, senator or congressman maybe. But I believe this exhibition fight is pure sports since the election isn't around yet.