> because sports betting is _not_ in the CFTC's remit

Traditionally it has not been, but the current CFTC says that 'prediction bets on sports' ARE under their purview. This has not been fully challenged in court, though.

If Congress intended for the CFTC to regulate sports betting, it would have had that language in the act that originated the agency. It's telling that only recently the CFTC has discovered such authority. No previous leadership of the CFTC read the act to mean what the current leadership thinks it means.