They allowed the pros to compete because many of them are drawing cards for audiences around the world. Given that the profit margins for every Olympics are very slim (in my homeland of Canada, Montreal has never entirely financially recovered from hosting the 1976 Summer Olympics), the IOC wants to make sure they can make money. Otherwise, they'd resurrect the anti-pro ban in a heartbeat.
They allowed the pros to compete because many of them are drawing cards for audiences around the world. Given that the profit margins for every Olympics are very slim (in my homeland of Canada, Montreal has never entirely financially recovered from hosting the 1976 Summer Olympics), the IOC wants to make sure they can make money. Otherwise, they'd resurrect the anti-pro ban in a heartbeat.