This seemed like more remain plotting to me from the moment I first heard it. Why would he do that? It would be contrary to the very clear Conservative manifesto, for which the voters have just delivered a strong mandate.
Their argument (it's not mine, and I don't believe it) is that Boris Johnson is an old-fashioned one-nation Conservative who, if his pronoucements over the years are to be believed, isn't actually anti-European and only jumped on the Brexit bandwagon as a means of becoming PM. Now that he is PM he'll revert to type.
My view is that Boris Johnson is cut from the same cloth as President Trump. He's a proven liar who will say or do anything to get what he wants. He has no fixed values or ideals and will assume whatever policies will deliver the biggest benefit to him on any given day.
Remainers never give up. Some remainer thought, "Let's spin the idea that now we've lost, we'll get what we wanted - and see if we can make the public believe that lie."
Even a "soft" Brexit is a million miles away from what this Remainer wants. For both personal and business reasons I want the free flow of capital and people within the EU and even a "soft" Brexit would see an end to that.