Lets not act like Southern Ontario isn't growing. We literally having a housing crisis because of the number of people moving here and the lack of places for them to live.
As far as their being a person or entity willing to put a team here, there have been many overtures made to the NHL over the years and the answer has always been no. Balsillie wasn't the only person wanting a team in Hamilton. Tom Gaglardi wanted to buy the Thrashers and move them to Hamilton, but they wound up in Winnipeg and he wound up buying the Stars. Who knows what would have happened if Glendale hadn't made two $25 million payments and they went to Winnipeg instead. Maybe Gaglardi would have gotten them.
There was also the Markham proposal, Remington who later bid for the Senators were behind that one. So there have been legitimate parties interested in putting a second team here. However, Bettman always shoots it down:
(this one in particular is annoying because he is cool with SoCal having 2 and NY having 3. Also the Chargers draw almost 70K fans a game even though the Rams won the Super Bowl the first year the Chargers were in SoFi stadium)
Despite all that the league's own internal analysis shows that a second Southern Ontario team would do well:
Judge muddies battle for Coyotes
So the bottom line is, Southern Ontario could easily support a second NHL team and even the NHL knows it but the NHL doesn't want to put a second team here for other reasons and has made that clear.