It was only ignored if they voted firstly not understand how parliament works, and secondly if they though they were voting FOR something. They weren’t they were voting against membership of the EU, the vote never said what would or should replace it. Turns out the only thing that could possibly replace it was Mays deal, which the ERG and DUP killed, or a CU /SM that the tories imposed their own red lines on to prevent going down that road which would have been an easy road with cross party support, again, to pacify its own extremes and the DUP.
Nothing like a PM ignoring an act of parliament.