why DID juice have his mental health problems?

im a massive juice wrld fan, love the new album, love the old ones, but the other day i was wondering why exactly he was depressed and stuff. people said he used drugs to cope, but what was he trynna cope with? now i get money might not buy happiness, but it doesnt get you sadness either. i know his dad left him, but i dont think hes carrying that into his twenties, so why was he so depressed? he had the money (not that money buys happiness, but it was a bonus), he had that lifestyle, he loved his job, he loved his fans, so what was wrong? what made him abuse drugs so much he practically only talked about them in a lot of his songs? just curious if anybody knows