I simply don't see it as Farage's success, at least nowhere near as much I do as Cameron's failure. Put another way, Farage may have been the one shouting the loudest about it, but victory in the referendum for him and his ilk could never have happened were it not for the cockiness and arrogance of Remain MPs and supporters in assuming that victory could come only through fear, or just that they would win inevitably so why bother planning for a "leave" vote?
Most evidence suggests that Farage himself, as well as UKIP, only ever had minority support -- even if you make the most generous assumptions about why UKIP didn't pick up more votes or seats in the 2015 election, it's pretty obvious that there are, and always have been, significantly fewer than 17 million UKIP supporters -- so that you may have to look elsewhere to explain fully the victory for the Leave campaign.
I suppose my final point is that, no matter the politician or the position they hold, it's much easier to convince people that you'd have done a better job if you're never in the position to do so. Considering the number of prominent Leavers who actually *have* been in that position -- and how successful they've been (ie, not at all, by anybody's standards) -- then I find it hard to take seriously the idea that Farage would really have been much better even if he *had* been given a shot. May has failed to get the Brexit you wanted, because that Brexit was impossible to attain, a position that, is essentially the same as Leadsom's, albeit for very different reasons.