Piggybacking from your thoughts a little, I think people Really overstate how effective Smash Bros. actually is as advertisement and that it is its divine mission to make games like Rhythm Heaven sell millions (which is something I'm seeing a lot thanks to the salt surrounding Ultimates DLC)Beneath the pretentious pseudo-epicness, that has come up quite a bit since Brawl, Smash isn't some kind of sacred Olymp of gaming, that validates a character's place in the industry
-Fire Emblem couldn't break a million worldwide and found itself dangerously close to being cancelled *after* getting a lot of love in Brawl until it got a new game with higher production values, waifus and newb-friendly mechanics completely independant of smahs. I also don't buy the "they brought the games to the west because of how popular Marth and Roy were" story when fellow Japan-only TBT game Nintendo Wars made the jump *without* smash. More likely, they wanted to replicate Advance War's modest success.
-Captain Falcon may be epic meme man but that sure didn't help his series.
-Being in smash didn't prevent Jigglypuff from becoming irrelevant in the game and anime for a long time
-Bayonetta 2 and its switch port didn't seem to get any notable sales boost from her inclusion in the game.
And that's just talking about playable characters. "Representation" through things like items and stages evidently did nothing for the success of games like Elektroplankton and Sin & Punishment 2. Mother seems like the only series that truly got a new fans from Smash and I have a feeling it would've been one of those games that would've seen a rediscovery thanks to emulation anyway.