So I went looking for ways to improve and here's what I found. Chess.com ...
Chess 2516 1 Ra7! 2 Rdd7! and 3 Rac7 mates. The black pawn is necessary, else there would be mate in two by 1 Kb4 Kb6 2 Rd6. With the pawn, 1 Kb4 is met by b2 and queening with check.