This position is a variation from the Lucena position when Black makes a suboptimal defense 1. Rc1+ Kd6. It's disastrous because it lets White slip his king off the e8 promotion square in such a way as to avoid check. The continuation:
- Rc1+ Kd6
- Kd8 Re2
- Rd1 Kc6
- e8=Q Rxe8
leaves white with an elementary King and rook versus king mate.