I actually used to work as a mechanic at a bowling alley while in college. Bowling is still popular on Long Island where I live but I think the demise of huge money pro bowling comes from 2 different aspects: 1. There are less amateur bowlers now and 2. Ball technology combined with illegal lane oiling patterns has made bowling too easy.

It was once a very rare feat to bowl a perfect game (300) Now it happens so much that when someone was on 10th frame carrying a perfect game I would not even bother to watch it. Bowling centers want to keep people coming so they make the lanes very easy with "walled shots" (no oil near gutters to allow for massive hooks). Now almost every reasonably good bowler bowls over 200 average, and the difference between winning or losing is much smaller to the point it becomes luck.

This is the same in the Pros minus the illegal pattern. So now there is much less differentiation between pro and amateur bowlers and it is hard to be consistently dominate as everyone is bowling very high scores. They need to make bowling more difficult again by regulating ball surface compounds more closely and making lane oil patterns more difficult. This will increase the divide between pros themselves and amateurs and make it more impressive to watch.