You mean aside from the feeling that the Leave campaign was built entirely on lies and spin, on telling people what they wanted to hear rather than what was actually going to happen, as evidenced by the fact that Boris and co are now desperately trying to force attention away from the promises they made or trying to make semantic arguments about how they're not really promises so they don't have to deliver on them?
I believe that views on immigration, regardless of motivation, were a contributing factor, but not the only factor. Not when you have outlets like the Express running with rampant scaremongering about just what the EU wants to do with your pension and crap like that.