TV Money. It's really that simple. I think I already explained this in the TNA thread but since Nitro the main revenue stream for wrestling promotions has been TV money. The traditional stuff like attendances, merch and PPV buys are obviously important and the more money the merrier but the real bread and butter is companies paying for the right to air your product.
TNA (like WWE) expanded internationally, and had TV deals in over 100 countries (I'm not sure how they're doing now because Anthem has been putting them on their own platforms internationally instead of negotiating with third parties) so they had money coming in from that. That money was enough to keep them going even when the revenue dropped after the Spike deal. Now they're owned by a media company that uses them to provide content for their networks.
Impact is alive because they, like other promotions, are beholden to corporations and not wrestling fans. So all the praise/criticism is irrelevant because there's only one audience that actually matters. They've always kept TV companies happy enough for long enough to keep them going and now they're owned by one so they'll keep going.
It's really not all that deep.