User blog comment:Fimber/Crazy things that would make sense... or so.../@comment-5674726-20131212001124

Question: why and in what way did he love Morgana so much and why did he hate Uther and Arthur?

Answer: he was Gorlois!

Makes more sense than the explanation we were given on the show.

I read one fanfic where Agravaine's loyalty to Morgana is rooted in his love for Vivienne; there was never anything physical between them but he loved her and, for her sake, he wanted her daughter to be happy, to the point where he was willing to support her shaky claim to the throne, despite having nothing in particular against Arthur. Still better than the Agravaine has a thing for Morgana explanation.