Rivals of Aether was basically the only Smash Bros-like that has ever been remotely good while also implementing its own ideas. No idea what 2 is like or why 2 is under a different company but the first was very popular.
The Steam store makes it look like Aether also developed 2, the only difference being that they outsourced “publishing” to Offbrand. AFAICT Offbrand doesn’t do development.