There were (and still are) more pro-UK/loyalist terrorist organisations in Northern Ireland than republican terrorist organisations. I have no love (whatsoever!!) for the DUP, they're a backward thinking bigoted party but unfortunately they're the only viable unionist party and as the people of NI are still of the us/them mentality when it comes to voting rather than looking at it from a policy perspective, it's the DUP (and similarly SF) that do better than the rest. There have been many many scandals over all sorts of things, the most recent being the DUP leaders involvement in a flawed heating scheme that is seen to benefit its party members and that will cost the NI economy a huge amount of money, however our politicians rarely resign and never get the sack, whereas if it was a Westminster MP they'd be out the door. Politics isn't working here at the minute and something radical needs to be done as we know what the alternative is and no-one wants that.
To be fair the DUP aren't the political arm of loyalist paramilitary groups though - their roots are in religion (which is where their views on abortion, same sex marriage etc etc come from). Their previous leaders were linked to a paramilitary group but the party distanced themselves from this when the group were caught importing arms from Libya. That said, paramilitary groups still hold influence in many communities and help mobilise the vote for DUP.