Manny has gone from being a degenerate gambler with a gigantic entourage who is incredibly generous on an immense scale to a born-again Christian who hands the money he would have gambled to the church and still pays for the entourage and every other fucker with their hand out. On top of this he's paying for multiple political campaigns.

It doesn't matter how much money you earn, you can find ways to spend it like water especially if you're not averse to giving it away.
But boxing can't be blamed for this. Larry Holmes invested all the money he managed to get out of Don King in property and is now worth tens of millions. George Foreman saved his money and was wealthy before the grill thing came along. On a smaller scale guys like Froch have kept their money and bought property and are now financially secure.

So you can't blame boxing entirely for this. It's still possible to retire financially secure even if your promoter is Don King. You just have to try and avoid parking your Bentley in the swimming pool and buying tigers and diamonds every day.