Real reason is males are mostly solitary and elephant territories are enormous. Being horny for months gives the males enough motivation to seek out the herd of women and children over the long distances.

elephants have an unusually long gestation period (and not just for their size, whales are typically only pregnant for about 12 months) Researchers think its necessary to give their brains time to fully develop, of which they have the outright largest of any land mammal and a body-to-brain ratio that rivals our own.

As for psychosis, I've been told that for people it typical lasts about a month from whatever triggers it. Maybe the bigger brain would mean it needs more time for the... psychosis(?)... to work through... whatever it's doing? Honestly, it's probably not whats happening with the elephants. They sounded superficially similar, so I made a glib comment about it.