Theresa May as home secretary as well as PM was also a freedom of movement (FoM) obsessive. Ending FoM was the star around which all other concerns orbited. Prioritising it meant leaving the single market (which has FoM as one of its requisite 4 freedoms).
So Poles out, Ukrainians in working under UAE conditions.
It’s no stretch to imagine she is saying one thing for political purposes (appealing to both anti FoM MP’s and anti-FoM voters) whilst helping engineer the deregulated post Brexit Britain her lobbyist funders request.
The ERG gambled correctly that they could get rid of May and get a deal that was more in line with their crazy ideology or go for no deal instead.
Like the labour party, the Tory party is a series of factions. Vote Leave leveraged the masses dislike of immigration to win the 2016 poll.
May’s deal didn’t appeal because it didn’t go far enough for these de-regulators.
They knew if Johnson was installed, they wouldn’t just get a different deal or no deal, they’d get a new government whose core objective was to pursue the implementation of this target.
/ends