It’s as simple as also making it a tv channel that one can pay their cable subscribers for. People who already buy all the channels they want from their cable company can buy that one too if they want it, while all those who do streaming crap can buy it direct from espn if they want.
From there, it’s up to the sports teams on that channel/stream to be interesting enough to warrant the money. But the teams and espn need to appreciate that this all could backfire. A customer might say “not only is this sports not interesting enough for me to buy this extra channel, I might as well cancel my regular channels if my team isn’t going to consistently be on those.”