The NHL doesn't have to grow the game in Toronto or any other Canadian city, teams like Arizona, Carolina, Florida, etc. need a superstar to hopefully fuel some interest and gain a bigger fan base.
Hopefully McDavid can turn a franchise around in the States like Crosby did with Pittsburgh
Carolina has already won a Stanley Cup in 2006 and had a Finals appearance in 2002. If anything that's what should grow the game down there.
Besides their 1996 Stanley Cup Finals appearance the Panthers haven't success like in a long time and I don't think McDavid would help that. I mean how come their other top 3 picks like Ekblad (1st in 2014) Huberdeau (3rd in 2011) and Barkov (2nd in 2013) haven't been able to get their fans out there. Plus didn't some people say them brining back Luongo would help their attendance because he was a very popular player his first time with them.
As for the Coyotes if the NHL wanted them to have someone save their franchise the smarter choice would be Auston Matthews who is from the State of Arizona and what better player for them to draft and market to their fans.
Finally if it wasn't for revenue sharing chances are the Hurricanes, Panthers, and Coyotes couldn't survive and they have the Leafs to thank for that from the money they get from them. So if anything the NHL owes Toronto for that and having them win the Draft Lottery to select Connor McDavid would only be a good thing for the NHL and they would make even a lot more money compared to him being drafted somewhere else.