I wonder the same.
I know a lot of people hate him, and I get it, but it’s interesting to me because it seems like the one relationship that has deeply affected Lana to the point of inspiring her last two albums (maybe 3 considering he got married while she was writing the new one).
She even said on the BB livestream last year she thought her world had ended when they split, and he broke her heart.
I think Text Book and BB are about him for sure, and he’s all over Chemtrails etc.
If you ask me, I think there’s a connective line between LMLYLAW -> Blue Banisters -> Tunnel. But it gets less direct and more existential.