bruh why not Bg2
Another
Actually it is a win for White because White has already captured Black's king. (Hey, if Black can start a move with thee pieces already checking White then it is reasonable that White already captured Black's king).
Must have been captured, otherwise the position would be illegal.
Four light-squared bishops are needed to do the job of checkmating the White king?
That a7 bishop seems to be lonely though. It does not wish to participate in the suffocation of the White king.