72-73: 12,516 (11th of 15*)
73-74: 14,162 (10th of 15*)
74-75: 13,444 (11th of 17*)
75-76: 11,963 (11th of 17*)
76-77: 12,259 (10th of 17*)
77-78: 10,501 (15th of 18)
78-79: 11,441 (10th of 17)
79-80: 10,024 (19th of 21)
(*No listing for Chicago)
Those numbers don't really support your comment of it being "revisionist history".
Look at the teams that were below them. Plenty are still around today. Nothing about their numbers says "unsustainable". Seals/Scouts/Rockies/Barons type numbers raise alarm, not 11k+, at least not in the 70s. By your logic, the Kings, Pens, Caps, North Stars, Bay Area, shouldn't be around anymore. Atlanta was well on its way to becoming a good middle of the pack city like the ones listed, but their owner went broke so hello calgary unfortunately.
If they were so well supported they'd still be there...and with regards to the Thrashers...their owners weren't actively sabotaging them until the very end. What sabotaged them was a lack of playoff hockey and a 4 game exit in their only appearance.
The Flames attendance was just fine. The problem was that their owner's real estate/construction business went belly up and he needed money very quickly. There were groups who wanted to keep the Flames in their rightful home, but the group in Calgary offered him nearly twice what they were. This is where the NHL should have stepped in and put their foot down, but they didn't want the Flames owner blowing the whistle on their stealing out of players' pension funds.
As for the Thrashers, the team didn't compete due to Don Waddell gutting their roster, as he was paid to. ASG never wanted to own a hockey team, plain and simple. Their goal from day one of ownership was to destroy it and only have their precious Hawks, who can't draw flies.
Atlanta fans are the NHL's biggest victims, they got royally screwed twice. Sad thing is very few people will ever acknowledge that, because "hockey doesn't belong in the south."