I don't think Nintendo has been treating like an underdog, they've called a major IP since 2016 after the success of Awakening and Fates.
https://mynintendonews.com/2016/04/28/fire-emblem-is-now-considered-a-major-ip-for-nintendo/
One of the last major Wii U games was an Fire Emblem spin off which just had a Switch port released yesterday.
Another spin off was released for the Switch in the first year of the console's life.
Three Houses was one of the first, first party's to be confirmed to be in development for the Switch.
When they announced the Feb 2019 direct, they flat out said there would be new info on Three Houses.
Fire Emblem Heroes makes more money then all of their mobile games by a wide margin.
I don't think Nintendo sees it as an underdog, I think they see it as one of their most important franchises due to its success last decade.