Bettman supporters keep saying how much the revenue has grown under his leadership while conveniently forgetting that every other league has grown its revenue faster than the NHL. As you say, the NHL used to be competitive with the NBA, and in fact, had higher overall revenue 30 years ago.
Bettman hid most of his underperforming league revenue by expanding the league. The new teams didn’t perform well, but they boosted overall revenue enough to let Bettman keep his job. Now we’re left with a league where 6-8 teams should die in order to improve overall league health. It’s unlikely that Bettman or any future commissioner will admit how massive the problem is, so we’ll just get teams that are always threatening to become bankrupt, dragging down the rest of the league.