Under the right setup, both the nba and nhl can work in the smaller markets example same owners. There is a false idea by a small group of seattle fans that believe that the nba will never return to seattle as long as key arena is the only option.
Under what setup would any of the small markets work well with a
terrible NBA team? After a brief relocation honeymoon, Louisville or Cincy will give a perennial loser the same level of tepid support as a Charlotte or New Orleans. If there's
also an NHL team splitting the market, it's almost inevitable that the market fails to support both teams -- and that goes double in a place like Nashville where the NFL is also in the mix.
This issue is clearly reflected in this chart:
List of American and Canadian cities by number of major professional sports franchises - Wikipedia
That chart is visually appealing because you can visibly see how the NBA and NHL have danced around each other to avoid sharing smaller markets. That is not random or driven by circumstance... there is a reason the NHL strategically picked places like Nashville, Columbus, and Vegas in its most recent expansions.
But MSAs are not really the best way to look at population... switch over to
a chart of TV markets, which better reflect the The smallest market in North America with both an NBA and NHL team is Denver, which is the 18th largest TV market (including Toronto). Over the years there has been a dance between the leagues around top-15 markets like Atlanta, Houston, Seattle... places where the leagues' failure to co-exist is more circumstantial than market-driven. It's clear that there is a range where the leagues are comfortable co-existing.
But once you get down to around the 20 range (Tampa and Orlando, extreme examples of Florida sprawl which changes the dynamic, show up a little higher) you very clearly see the divergence. The highest-ranked TV markets for an NBA relocation would be St. Louis and Pittsburgh, terrible choices from a market-saturation standpoint. The first city with a growing economy and little market competition is, I guess, San Diego? Or Kansas City? Those teams won't support a
terrible team either, hence nobody jumping on an NBA team to relocate there. It would be just as well to stay in an Orlando or Charlotte and try to make it work.