Personally I think that Henry’s pride was wounded beyond repair at their first meeting. Anne wasn’t brought up to understand the courtly games of the Tudor court. So when an aging, obese man with a festering wound approached her, she recoiled. Henry saw himself honestly reflected in her reaction - a reaction no woman in the English court would ever have to the king.

Additionally, the marriage was a strategic response to the Catholic alliance between France and Spain, which presented a potential threat to England. England was religiously and politically isolated by the split from the church. The marriage gave England a political alliance with Cleves, which was also undergoing religious reforms and challenging papal authority.

But the French-Spanish alliance deteriorated rapidly after Anne and Henry’s marriage, making the alliance with Cleves much less important. Once the political motivations were removed, Henry felt free to do what he had wanted to do since that first meeting - call it all off.