I headcanon that when Bettel and Flayon showed up in Xenokuni, Hakka got the worst case of snowfever recorded in history and wanted to make the clown his husband, so to receive the blessing from his father and tribe he had to find a way to prove that Bettel would be able to defend and care for Hakka. So Hakka had to set up these super elaborate traps that would make it seem like Bettel had saved him from a wild animal when in reality he had already killed the animal and simply staged it so that it would look like Bettel had done it.
Now that Hakka had the blessing to marry Bettel, there was no reason to postpone the ceremony but it was also the first time that Bettel had heard of it and didn't know what he was getting into when, as tradition demanded, he had to fuck Hakka in front of the elders of the tribe and Flayon who was biting on a handkerchief while watching the whole thing, screaming "it should have been me" internally, giving a display that would be absolutely miserable to anyone else but Hakka.
This is why they divorced the instant they returned.