Election means delay. Delay means more pressure on Theresa May.
Irish government cares less about the North-South customs issues but is very concerned about a customs barrier across the Irish sea and how Irish trade will be effected by that. It's using the North-South issues to pressure the U.K. to remain in the customs union with the EU (like Turkey is).
The election is orchestrated to turn the pressure up on the U.K. by putting the caretaker government in a position where it cannot green light anything.
One massive stroke. Think about it.