If the Remain had won the referendum the result would still be non-binding.
Cameron should have clearly defined the parameters of the Referendum and made it a binding referendum. He did not, which is why there is debate over what this means or does not mean.
He should have also specified exactly WHAT leave meant - whether no-deal or customs union or something in between. He did not, leading to the mess we are in now.
And your statement “Everyone accepted the legitimacy of the referendum and the determinancy of the result “ - is false — people were asking at the beginning what Cameron was up to creating such an ambiguous referendum question
“people were asking at the beginning what Cameron was up to creating such an ambiguous referendum question”
It wouldn’t have been “ambiguous” if Remain had won.