Rd1 loses the initiative. Your rook was already well-placed on f1, putting pressure on the f7 pawn. By moving it to d1, you've abandoned that attack and the rook now has no clear target on the d-file — the black king on d5 can simply step away.
Better was Rd2 — keeping both rooks connected and preparing to double on the d-file or swing to the kingside. At your level, a good rule of thumb: don't move a piece that's already doing something useful.
Why not Rc1?
Show me the f7 idea
What's "connected rooks"?
