Oh and imo: hell (Mephisto's not Hela's) would freeze over before Odin ever ever gave Loki the throne willingly.
I don't really see the point of view that it is "easy" to explain Loki on the throne; there are so many obstacles. I also don't think it's repetitive to have Loki on the throne again, as it is in totally different circumstances. He is not rightful, he is not open about it, everyone thinks he's dead, everything thinks he's Odin, Thor feels favoured and does not want the throne (yet). Total wildcard plot device. Well played. If you find that boring, sucks for you.