The same year the Yotes were also threatening to move, but Glendale gave 50M plus a 15M a year contract and they had an arena. So the NHL hold on to them.
There was no City support in Atlanta. The ownership group had been trying to sell for years (since they bought it actually) and couldn't find anyone willing to buy the team for 110M. Technically, it would have been possible for the NHL to buy a second team, but they would have needed to play in (what's now) Gas South Arena. But think about it, they couldn't find a buyer for 110M, how would they find a buyer for 110M willing to also spend +300M to build an arena? The Yotes had the arena and the NHL can always make a shady deal to have a puppet owner until a real lol one comes by, no such luck for Atlanta.