I believe May was trying to make a trade deal with the remaining EU nations, and the Parliament was balking at the terms the EU insisted upon. The Parliament has been insisting on some sort of a deal before dong the actual "Brexit," so there was an impasse on that and Brexit languishes. Johnson was elected on the promise that he'd Brexit, deal or not, and that's the 10/31 deadline. My guess.
@Sighlass @Cyber LibertyParliament did not pass any plan to present to the EU; the two sides could not agree on a plan. May quit, now there is Johnson and he can't get both sides to agree, either. One side wants to exist the EU without a plan; the other side wants a plan or stay in the EU.
Here is one change that would happen if they exist the EU:
Right now, anyone in these countries can do business in any of the countries as though they live in that country - no restrictions, no paperwork to get permission to work there - it is a single market comprised of all the EU countries.
My son owns a documentary film company in London, and he can take his camera crew to any of the countries without notifying them he is coming - no paper work to turn in, no approval to get before going there; it is as though all EU countries are one country.
If Britain leaves the EU, son has to notify any of those countries he is coming there to work and detail what that work is. That country government will then decide if he can come there and do work. This is one reason businesses do not want to leave the EU; they are trading now as though they are in one country, meeting the standards of the EU. Once out of the EU, they must meet the standard of each country separately.
"The House of Commons Library has said that the overall impact of leaving the EU on businesses isn’t really about the impact it will have on the size of the ‘burden’ regulations create. It is about whether the benefits of having a more tailored and flexible national system of regulations outweigh the
loss of access to the single market that may come with whatever relationship we negotiate with the EU."