Okay so here's the thing. The problem isn't that Nintendo doesn't want to support smash. The problem with smash is all the crossover characters.
Nintendo does actually own the rights to all the characters in smash. Like sonic, Terry and Solid snake for example. Because of this it becomes a " liscencing" issue. For Nintendo to actively make a " smash" tournament , the would need to negotiate additional contracts with every company that has one or more characters that doesn't belong to them.
This same issue can be seen with games like Marvel vs Capcom and Dragonball fighterz. It is not as simple as simply wanting to make official smash tournaments. Every company would want a piece if the Pie.