The Weiders already got their money out of bodybuilding to the tune of hundreds of millions of dollars as they sold off pieces of their empire over the years. I'm sure the money is safely invested in non-bodybuilding industry related securities.
I think Ben just hangs around because he likes looking at muscular men in speedos.
Manion is the one whose income depends on bodybuilding. The NPC is his "family business", and it is vital that the IFBB is run in a way that protects the interests of the NPC.