Why was Edward VIII‘s marriage to Wallis Simpson (a twice-divorcee) such a big deal religiously if the Church of England was founded on the basis of Henry VIII wanting to divorce Catherine of Aragon to marry Anne Boleyn? I don’t understand why there would be an Anglican Church rule banning marriage of a divorcee when their ex-spouse is still alive if the only reason Henry VIII broke with the Vatican (and therefore create the Anglican Church) in the first place was to divorce his wife and marry another... Catherine of Aragon was still very much alive when Henry divorced her and married Anne, which was the whole point of creating the Church of England.
I have actually answered a similar question before! To repost it below:
The operative difference between these situations is that one involves a foreign, "ruined" woman marrying a royal man, and the others involve royal men being involved in extramarital relationships. It did not matter what Edward VIII did, sexually, himself - it mattered who he married.
Basically, a marriage and an affair are two very different things in English history. When a king or prince married, he brought his wife into the royal family - unless he were a younger sibling, she would become queen consort. Given ... the patriarchy, women's virtue was seen as a reflection on their families of birth and marriage, and queens consort had to be as morally upright as possible. The role of the English queen was to be the perfect counterpart to the king, to engage gracefully in social and ceremonial events, to deal with ambassadors and other foreign visitors, and to bear heirs that were unquestionably her husband's. A mistress had none of these responsibilities, because she filled no ceremonial role at court and was not legally tied to the king. While a king's or prince's peccadillos could cause gossip, it ultimately did not matter that much if he engaged in extramarital affairs.
William IV's long-standing relationship with the actress Dorothea Jordan was almost a marriage - and would have been, if George III didn't have the power of veto over who his children married. The king would not allow an actress (considered, at the time, as little better than a prostitute) to marry into the royal family, draw an income from the crown, and give birth to children who could potentially inherit the throne. He became king because the people in line for the throne before him died, and when it became clear that the crown would pass to him (after the death of George IV's daughter, Princess Charlotte), he married an "appropriate" consort, a German princess. His legal right to the throne was much more important than his personal morality - and in the early 19th century, behavior that proved a man's virile heterosexuality was generally good for his reputation, and the church would turn a blind eye. Sexual continence was for Georgian women.
Edward VII grew up in the shadow of his mother and father, Queen Victoria and Prince Albert. Their legendary fidelity and happy married life did affect the idea that being faithful in a marriage was only for women, but Edward chafed under his parents' expectations, and had affairs from a young age. He was discreet, although society gossip did find out about many of the women he consorted with, and he did not acknowledge any illegitimate children. His wife was a Danish princess, another appropriate choice.
So when Edward VIII prepared to marry Wallis Simpson, the real issue was her sexual behavior, her divorce, and her origins. The Church of England reluctantly allowed remarriage after divorce, but frowned heavily on it, and as it is the state religion, he was expected to follow its publicly-visible tenets as closely as possible. Wallis was not only a divorcée (in a time when divorces were still fairly scandalous), but a double divorcée with two living husbands. She was also foreign and not a princess, where precedent was for English royalty to either marry foreign princesses or titled Englishwomen: Americans rich from trade did not come into it. The two had also been involved in a long sexual relationship of the sort that was acceptable between a prince and a mistress, but not a prince and a future wife; she also was believed to have slept with other people while she was in the relationship with him. Basically, Wallis Simpson didn't fit the expectations for an English queen to any degree, and the church was far too hidebound to accept the entire package - it was threatened by her, and there was no cloak of propriety that would cover all of the problems. The public wasn't confronted with Dorothea Jordan and Lillie Langtry as the consorts of their king but as actresses, whereas they would have seen and heard about Queen Wallis the Divorced very, very frequently. It's also important that the aristocratic and governmental class as a whole disapproved; he didn't abdicate for her just because of the church, but because pretty much everyone in power was against the match.
In that previous answer, I didn't mention Henry VIII, but as you asked: Henry's "divorce" was actually an annulment on the grounds that his wife was legally/morally his sister, since she'd been married to his brother, which was against the church. (Both the Catholic Church and his breakaway sect.) They had been given a dispensation by the pope as she swore that the marriage hadn't been consummated and therefore wasn't completed and "real", but Henry accused her of lying decades later. It was a totally different thing than a pair of secular divorces, even without the double standard issue.