Help me understand puzzle

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2flyguy
I don't understand how black rook taking c5 rook is not the best move [Site "Chess.com"] [Result "*"] [SetUp "1"] [FEN "2rqr1k1/pp3pp1/4p2p/1R1nP3/3P4/1Q3N2/P4PPP/5RK1 b - - 2 19"] 19... Rc3 20. Rxd5 Qc8 21. Rc5 Rxb3 22. Rxc8 Rxc8 23. axb3 *
BigDoggProblem

Either way, Black is down a Knight and has a losing position.