He named it. The pound dropped eating his margins. So he moved to a better place with a stronger currency and culture. He will not be the only one, almost everyone will be fleeing soon.
I'm sure the real reasons are political rather than financial.
He’d be earning less — as the article mentions — if earning in pounds and paying out (to subcontractors) in other currencies.
He did say he's originally from Yugoslavia. Since the Brexit vote, the UK has become a lot more hostile to immigrants. That can certainly be a good reason to leave too.