Good question. What we've learned since then, watching the parade of human folly, is that they didn't sacrifice their lives in error, either.
Someone up-thread was trying to make hay out of the idea that, over the centuries, judgments of nullity were at times bent by political considerations. I wouldn't be surprised. Interesting for the historian or the novelist, but irrelevant here. In moral terms, Henry's case wasn't a close one. It was as cold-blooded and venal as it was logically ridiculous.
The issue with Henry VIII was not that he got an annulment. Because of consanguinity laws in place (Catherine was the widow of Henry's brother Arthur, making her off-limits per the laws in place at that time), Henry had to get a Papal Dispensation (an official determination that justice mandates an exception to the law) of those consanguinity laws in order to be able to marry her.
Then he was to ask the Pope to basically say, "oops -- never mind," in regard to his prior dispensation. Obviously, that's not going to work as it would call the Pope's judgment into question for all manner of decisions.
That's what made this different than other annulment situations.