I don't even play every month but I can see why it's winning, went down the rabbit hole a little bit and the data is telling.

passed tennis in tracked activities on apple, growth rate is insane

I think tennis barrier to entry is too high for most people. Pickleball is fun for any skill level so I think it follows that total addressable market is bigger.

The most convincing stats for me were that top player salaries and sponsorship are climbing towards tennis pretty quickly and that the average age of the pickleball player is lower than tennis.