I'm going to assume you follow one or both, and that you're aware of the high prevalence of PEDs in both.

Now how are Olympic sports different than those leagues? Is there less of an incentive to cheat? Is the IOC more interested in preventing cheating? Do the athletes not care as much?

If anything, there is likely more doping in the Olympics because you have the resources of state actors backing athletes, see, e.g., Russia.