A deep concept | Puzzle of the day 10/14/2023

I still don't understand why Ra1 is considered good. We are essentially making our white rook useless and passive.
I still don't understand why Ra1 is considered good. We are essentially making our white rook useless and passive.
Yes, it seems strange to leave the Tower there. White's idea is to prepare the a4 move, trying to open the a-file, or cause some weakness in Black's queenside pawns (for example, if Black answers a4 with ...b4, the a6-pawn is more easy to be attacked). And although Black has an open file for his rook, there is no way for him to enter White's field with that rook (which is the main objective of having an open file).
But it's not like White's plan gives an advantage, according to the engine. But I found the idea interesting.