I've heard before that a lot of copyright enforcement bolsters your arguments in court by demonstrating the value/unassailability of the brand. Like, "we sued everyone who made garfield shirts without permission and this is no different." Letting stuff slide means missing an opportunity to build precedence, I think?
so i think it's lawyers doing what could amount to "routine maintenance" by being overzealous. The possibility that Nintendo could try to cash in on excitebike one day means that a passionate fan doing a remake in another engine is a Potential Threat
It all still boils down to "they trying to capitalize on nostalgia and want it to be impossible to get your fix anywhere else." But I think this might explain why they're such assholes about it. Possibly. This is speculation
Oh also like...I couldn't tell you exactly how, but I feel like one element that must be in play here, is how instrumental the donkey kong lawsuit was to their history.. Like when you think about how Kirby got his name, and then consider how incredibly important and valuable their IP is, it does make a bit more sense.
Not less shitty. But if we're looking for an explanation.
e: oh right, and they're about to move onto a new console, and uh, i feel like the disaster of the wii u made nintendo even more obsessed with the bankable ip that saved them. They're about to enter a new era and things could go very wrong. Nintendo often comes off to me like an incredibly paranoid and aggressive dog refusing to let anyone near their bowl. It must be terrified of starving, if it's snapping at so many friendly faces. I dunno. They suck but this is about why they suck, right?