It’s hard to pretend this isn’t at least gambling-adjacent when most people are simply betting on outcomes.
It's gambling sure and gambling should generally be legal. People are bizarrely puritanical about this.
It’s easy to pretend, just really hard to convince anyone without a direct financial interest.
Given that exactly the same thing has been regulated as gambling in Europe under the name "betting exchange" for 25 years the case for it being gambling is quite strong.