Based on what I recall about Atlanta moving to Winnipeg, the only reason it happened was because the NHL and Atlanta ownership had thoroughly exhausted any and all possibilities of keeping the team in Atlanta. Once it was accepted that there were no potential owners who were able to keep the team in Atlanta, that's when the NHL allowed ownership bids that included relocation to jump in.
Not true. Atlanta's ownership never meaningfully attempted to find someone interested in keeping the Thrashers here, as they wanted the team out of their building from day one. There were multiple, credible people/groups interested in buying all three assets (Hawks, Thrashers, arena), but Atlanta Spirit Group had entered into a sham exclusivity agreement with John Moores, the former owner of the San Diego Padres, for the sale of the Hawks and arena, which prevented anyone from being able to buy all three and effectively isolated the Thrashers for relocation. Not coincidentally, that exclusivity agreement ended the day the Thrashers were sold to True North. Beyond that, ASG made it clear it was unwilling to negotiate lease terms with any Thrashers-only prospective buyer, leaving them with no place to play even if a buyer wanted to keep them here.
The NHL did nothing to step in and thwart ASG's malfeasance. My opinion is that the league preferred to sacrifice Atlanta if it resulted in ASG going away. The league didn't want to get sued by those clowns.
Atlanta Spirit Enters Exclusive Negotiations For Hawks With John Moores