Sports gambling a few advantages over any other subject that seem near insurmountable to me:

- it has the semi-respectable veneer of something that normal people have done throughout human history

- it has completely parasitized existing sports media to target new users in ways that aren't available for other topics

- some variant of 'sports' is happening 24/7/365 with enough prop bet granularity to capture the full attention and disposable income of addicts. There's an ongoing controversy with a star college football quarterback who was going to MLB games to place bets on every single individual pitch.

You can basically think of gambling addicts as a finite resource that these different companies are competing for. Many people get addicted to lootbox/gacha games at an early age, and even larger portion are already deep in sports gambling. The target demo for non-sports prediction markets roughly matches to people in earlier times who got into commodities futures or optimal strategies for casino games (which clearly existed but never at a scale to rival what we see with sports betting right now).