It might (help) do for the Tories if they end up having to hold another GE – and it seems likely that they will have to at some point. Though on reflection it seems they had no good options – fundamentally if they can’t get a queens speech passed then they either have to hand over to Labour or call another election. It might just be possible they could get a queens speech passed without DUP support, but if not the DUP they would then be relying on support from parties who don’t naturally support them (at least for them not to vote against it).
So the possible options:
1) call another GE – bad, bad, bad for the Tories (in the short term)
2) attempt to pass a queens speech without any formal support from another party – a big, big gamble, one which is likely to backfire and force one of the other options anyway
3) tell JC to get on with it – the worst possible option in the opinion of those in control of the Tories (though he might also struggle to get a queens speech passed, even calling in all likely support)
4) get the support of somebody other than the DUP – seems incredibly unlikely
5) make a deal with the DUP
Looking at that list of possibilities, they probably picked the only possible option for them to retain power, at least for a little while. In the medium term they may end up wishing they’d just called another GE and got the pain out of the way without damaging themselves further.