what would they have done if it was not being streamed on bet365 they would have had no way of seeing this match at all barring going to the match. I understand what your saying but just because it available doesnt mean you have to use it. There are untold thousands of recreational gamblers who maybe dont have the chance to go watch the teams they follow for a number of reason can now enjoy watching there teams.
I think its quite the opposite, the tv rights hasnt really changed in terms of the amounts of matches that bt sport and the bbc show. Bet365 having the rights to stream matches actually means that matches that would never have been televised in the first place are now available to be seen. It would be a different story if bet365 had exclusive rights to the fa cup and was the only platform to be used.
Was at a stag do in liverpool a few years back and went to buy a few cider for sitting in hotel room, cider came to £3 wanted to pay by debit card, guy said minimum spend £5 so got 2 lucky dips to make it up to a fiver, first line won a tenner and on the second got 5 numbers thought i was rich to find out it was only £2500 not bad for something i hadnt intended to do in the first place