i couldnt be more obvious that sasuke let himself be stabbed so he could be in a near death state to awaken his own rinnegan. he knew that the chakra he just got from hashirama along with his own uchicha dna and himself being near death would be the key to awaken his rinnegan. If sasuke was serious he wouldve used his perfect susano to pulverize madara there is really no denying this.