It's far and away the most generously treated series in Smash when factoring in it's popularity.
In Ultimate. In Smash 4, out of all the characters they could've chosen, they thought FE needed it the most.
It was one of three series to get it. Another being Uprising which also has tons of evidence of bias towards it.
The amount it has is tied with Mario. It's also suspect that Corrin got their own, when they are supposedly a character that Sakurai was forced to add in.
You're looking at them individually, and not as a whole. Sure when you look at them one at a time you can think of a few other series that have similar stuff, but for it to happen so many times for a single IP is when it gets suspicious.
I made my point earlier about how non character content is basically nothing compared to character content. If it wasn't discussing stage lists for competitive smash I'd doubt they would get any significant amount of discussion whatsoever. Same could be said for Assist trophies and items.
If FE fans really felt they were super significant. then where was the hype for the katana, seeing as its FEs first item? Why was a clone of Roy, who was a clone of Marth much more hyped despite FE fans getting new characters many times before?
The dirty secret about Fire Emblem getting the Guidance was there weren't really any other candidates. To have a cameo in a Guidance or Codec, you have to be from a series where the characters frequently speak in fully voiced sentences in an intelligible language. It would be strange to have the fully voiced Kid Icarus cast interacting with the Godzilla-grunting Bowser. There's only three series that meet this criteria: Kid Icarus, Star Fox, and Fire Emblem. Kid Icarus doesn't work for obvious reasons, while Star Fox had a cameo in Brawl and it wouldn't make much thematic sense for the Sci-fi characters of Star Fox to be talking to the Greek Mythology-based Kid Icarus cast. As such, it was really either a Fire Emblem cameo or nothing.
Similar thing for victory quotes. Star Fox, Kid Icarus, and Fire Emblem are the only series that have their characters speak in fully voiced sentences in a real language, so they're the ones that get unique victory quotes. It's not that special to have Link or Donkey Kong grunt in a slightly different way when facing another character from their series.
Honestly, Fire Emblem having two unique victory themes makes sense given the context. Characters mostly get unique victory themes when the standard series doesn't really fit them. Villains, for example, have a unique theme because it's kinda weird to have Bowser, Ridley, or K. Rool celebrating to their enemy's theme. This generally applies to Corrin, seeing how Lost in Thoughts All Alone effectively replaces the standard Fire Emblem theme throughout Fates. It's a little different for the Awakening gang, but that more likely has to do with there being a large number of reps from that particular game. If we lived in a world where Lucina stayed a Marth costume, echoes never became a thing, and Robin was our only Awakening character, he'd probably just use the standard Fire Emblem theme for his victory.
Besides, I don't think Sakurai really cares about victories too much, seeing how Chrom initially had the standard theme and no one caught this until fans starting noticing on the internet. Also, I never said that Sakurai was forced to add Corrin in, but Corrin was in the right place at the right time to fill a DLC quota. I'm sure Sakurai likes Corrin, but I don't know if he would've joined the battle if the very specific set of criteria that got him in wasn't in place.
That being said, even though the fanbase seems to treasure fighters above all else and views them as the series' worth in the context of Smash, I don't think that's how Sakurai sees it. If Sakurai thought that fighters were the only thing that mattered, why would he put in so much effort to develop new items, stages, and assist trophies? Likewise, why would he take so much time to show off various items and stages during the game's pre-release? Fighters may be the meat of Smash Bros., but a meal with only meat is kinda boring. You need sides to add some additional flavour, Smash wouldn't be the massive game it was without things like stages, items, music, or assist trophies.
