At one point he was considered to be one of the best players at his age group, then he moved to Monaco and I haven't really followed him since. I'm guessing he didn't do too good there, but that being said Monaco are a mess these days and almost nobody does.
no idea what happened there with him, like you, not followed him since he went there. Thought it a weird move really, considering his age. But yes, he was hugely rated, maybe all went to his head a bit.
Time for a bit of a re-set for him, and playing on a talented team, who are in the CL, for a very good coach, should serve him well.