He was pressured not to marry Wallis Simpson. If he married her it would have been a constitutional crisis, so in order to prevent that controversy, he abdicate

He was pressured not to marry Wallis Simpson. If he married her it would have been a constitutional crisis, so in order to prevent that controversy, he abdicated and married Wallis Simpson. He could have chosen to be the king and not marry her; or he could have married her anyway and embrace the huge controversy. This is why I said "he abdicated in order to marry Wallis Simpson without controversy".