Golden rule of warfare and politics.

Open up another front.

People now have to deal with this and put aside the machinations of Brexshit. When the full import comes home to roost, and the mess may be temporary (say 10 years or 30 according to some female politician) there will be other fronts opened up. Distractions, "good days to bury bad news" kinda stylee (all Govs do it).
At the moment it is a Tory leadership thing, but at the end of the day there will be loosers, and more of them than not. And it will need a huge propaganda machine to ameliorate the ire of those who will see what they are loosing. Yea yea there will be gains, small beer to latch on to. But the pound in your pocket is already devalued. And even the governor of the Bank of England is warning which way the pound will take - a pounding.

The reason for 70th and not 75 or 100 is.......... see above.