Hung Parliaments can do exactly what the Conservatives have done, to make up the seat numbers, ask a minority party to join them.
Now, people, especially Labour voters may not like this ( DUP) but it is legal.
The only question in this case, is does it breach the Good Friday agreement?
I imagine not, or would it have gone ahead.Yes, the Conservatives could have soldiered on without the DUP or anyone else, but nothing would have got done, all their policies would be voted down ( including Brexit deals) and there would have been another GE called within months.How would any of that be good for the UK meanwhile.The Markets hate uncertainty.