Corbyn's "conversion" to Remain was sincere
Not a hope in hell. He was (and still is) opposed to the EU as a body because it's not rules by the proletariat.
His apparent conversion to Remain is purely to try to make him different from the Tories (which appears to be built into his DNA).
clearly a weak/incompetent leader
Like most people with strong beliefs and opinions who have spent most of their lives as outsiders, he's really, really not good at consensus politics. It doesn't help that he's hated by a large portion of his own party..