I learned a little more recently.
The lich assaulted the wedding because...
The person playing the lich was the boyfriend of the person playing the girl getting married, and she went along with this to shut him up since he was complaining about her 'romantic' RP with Paul's character.
This person is part of a long distance romance with the girl (and is now the 'ex boyfriend'), and would talk with her OOC only once a month, if that, and would rather talk to other people on the server.
But since he was getting in her face, she decided to let him run a scene to 'delay' the wedding some.
That is the only reason the lich showed up.