His cabinet exploded. Repeatedly. Like, it was pretty specatacular. His minister of something or other (or maybe his chancellor, I don'tknow) was one of the ones who resigned. Then two days later, the person he named to replace the former minister then called for Boris to resign.
Wash, rinse, repeat x 40.
Some ridiculously awkward meetings with MPs were shown saying he's politically dead and he kept saying "Nah" (and that's only a slight simplification of what he actually said)
Today he said he intends to resign. Which is interesting because I imagine it's about 50:50 whether he actually intends to. He said he wants to wait until a new leader is chosen.
There are also rumors of him trying to call an election or even the queen getting involved. Which would be extraordinary.