If I am not mistaken he was classically trained.
He long ago passed the point where he needed to sell albumns, so that’s when they start doing projects they want to do, and since these often are not mainstream they tend to not sell and their pop careers slowly end.
Every year’s a souvenir, that slowly fades away...
Joel was unique in that he went out on top. His last two studio albums (Stormfront in 1989 and ‘River of Dreams’ in 1993) were huge sellers. And he’s still very popular.
His piano teacher was a Julliard GRAD.