From Farage’s point of view it makes complete sense - Boris’ deal would most likely get the muster to get through parliament - he would get most of the Tory votes + a large chunk of Labour MP votes.
If Boris does that and gets a deal by october 31, he proves that
1. He delivered Brexit by 31.October
2. He got the Northern Irish happy
This would then destroy the Brexit party, just as the Tories earlier moves in 2014 destroyed UKIP (Farage’s previous party) in the 2015 election.
But if Boris delays Brexit then his chances for re-election are destroyed and Farage gets the upper hand for his party (as he then has a source of outrage).
Boris is in a bad position to negotiate a deal, when he’s seemingly forced to accept any deal the EU gives him.
He would be in a better negotiating position after a Oct 31 “no deal” crash-out.
The discussion so far has all focused on the economic pain that would be felt by the UK, and no attention on the economic pain felt by the EU were it to suddenly lose tariff-free access to the UK market.