Right. Henry actually got a dispensation from the Pope to allow him to marry his dead brother’s widow. This was against the law of the Church, but not that of the Bible, which in the OT actually required a man to marry his brother’s widow. The story behind the Book of Ruth.
So when the Pope denied him the right to divorce her, he fell back on the notion that the Pope had no power to allow him to marry her in the first place, from which it’s no distance at all to the idea that all the Pope’s claimed powers are illegitimate.
Wolsey and Henry devised the first strategy; Cromwell and Henry devised the second. Only one out of the three lived to a relatively old age.
Yes, it was considered incest in England to marry your brother’s spouse. That was not the case in Spain or France, I believe. Remember, these countries all had laws that differed from each other and sometimes from the Church.