In an interview with the Guardian yesterday he said:

Sheeran says of his label: "They were really, really against Galway Girl, because apparently folk music isn't cool. But there's 400m people in the world that say they're Irish, even if they're not Irish. You meet them in America all the time: 'I'm a quarter Irish and I'm from Donegal.' And those type of people are going to fucking love it. My argument was always: well, the Corrs sold 20m records. The label would say, 'Oh the Corrs, that was years ago,' but who's tried it since the Corrs? There's a huge gap in the market, and I promise you that in two years' time there will be a big folk band that comes up that's pop, and that will happen as a result of labels being like: 'Oh shit, if he can put a fiddle and uilleann pipe on it, then we can try it as well.'"

Which could be interpreted as a purely commercial gesture: tapping the Irish diaspora. But YMMV.