The disbelievers prevented you from performing your pilgrimage and sacrificing the animals, where they should be sacrificed. Had there not been certain believing men and women (in Mecca), whom you do not know, and the possibility of you killing them unintentionally at the midst of the confusion of the war, God would not have stopped your victorious capture of Mecca. God prevented the war [among other reasons, to give more time to disbelievers to weight it out and] to admit into His Mercy whoever He desires. If the believers were not in the middle of disbelievers, God would have severely punished the disbelievers.