This is the position after 1... Bb4:

after 2. Kh1:

and after 2... b1=Q#

How are you proposing that 3. Rxb1 is going to happen?
This is the position after 1... Bb4:

after 2. Kh1:

and after 2... b1=Q#

How are you proposing that 3. Rxb1 is going to happen?