I think the NHL Board of Governors had been pushing to have those teams move for years. The four franchises that came into the NHL as part of the 1979 merger agreement with the WHA were never really a top priority of the NHL. The immediate success of the Edmonton Oilers (through their sort-of-underhanded methods) probably caught the NHL leadership completely off guard.
Always the weird part with that chunk of NHL history. Many different forces. In the end though those teams moved on ownership decisions. And now Winnipeg is back, but no good. I know they inherited a bad team from Atlanta, but they need to get it together.