TBS isn't a dead network. It has more original programming than USA and TNT and their highest rated original shows are perennially in the top 15 of cable ratings.That's exactly what it was. They threw AEW some incentives to move, so the optics wouldn't look like they are kicking AEW from their time slot in exchange for the NHL. That type of thing happens in the business world all the time to save face with all parties involved.
TBS is a dead channel that mainly only shows reruns, so they could afford to throw them an extra show as any ratings from it would be way better than what's being current generated.
Getting Dynamite will be a positive for TBS because it is higher rated than most of the stuff they show besides Star Wars flicks but that metric applies to a lot of the shyt on cable TV right now.