He’s been writing classical music. He got bored with pop songs.
He hasn’t even been doing that. One classical album came out in 2001 and that was it.
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...