"If Remainers had got behind the decision..." -- that's a very confusing statement. What, are we supposed to have abandoned what we argued for? Would Brexiters have, were the result reversed? Of course not! Why should they?
But, even setting aside the fact that democracy is defined by the losers being free to continue to argue their case, rather than vanishing quietly into the night -- even setting that aside, there's a further problem with that argument: namely, that Brexiters are the ones responsible for carrying out what they voted for, and for showing their arguments to be correct.
Stop blaming Remainers for the failures of the Brexit camp. Johnson, Davis, Fox, Gove... many others besides, all at the top. And all of them have failed to deliver what they promised. That's on them. Even May assumed office with a promise to carry out the will of the people, and despite the ridiculous conspiracies AB is now spinning, she spent at least the first year or so doing that wholeheartedly and enthusiastically. More so than any of the actual Brexiters, most of whom have restricted themselves to heckling from the sidelines.
I've no doubt that, given enough time, enough planning and enough care, Brexit need not have caused chaos even in the short-term (although I would still have held it to be the wrong decision). As it is, a vote was offered to the public to kill the issue, the public didn't do as it was told -- and now the government's trapped into delivering an utterly impossible task in far too little time against all its better judgement.