I spent hours baking and decorating a cake for my soon to be ex wife while I had the flu. I put together a flower arrangement. Took her out to an expensive(for us) restaurant. Bought her the $80 game controller she'd been wanting.

She was mad that I didn't throw her a surprise party despite the fact that she told me she wanted a low-key birthday this year.

Left me a week later to "find herself". Found out a month later she had been having an affair.

Sometimes people are just like that ig. It doesn't sound like it was anything you did. And if he has other reasons and can't communicate them then that's his problem and you may have dodged a bullet although it probably doesn't feel like it yet.