So, trying to summarize:
-More than 6 years ago, the party in power was afraid of losing the election due to the relative growth of a minor "fringe" political party in Northern Ireland.
-Therefore, the PM at the time thought a good way to appease them was throwing them a bone: in this case, a Brexit referendum. The gig worked and the party held the majority and won the election.
-One year later, the Brexit referendum spinned out of control, with blatant lies and disinformation running rampant and even an MP killed during the campaign. With nobody on the breaks and on the birth of a new kind of election to which nobody was prepared for, Brexit won by a very small margin.
-Having spectacularly miscalculated the effects of his move, the strongly anti Brexit PM makes a last act of cowardice and resigns, leaving a path for the pro Brexit faction of the party to ascend to power.
-A new PM arrives, and it somehow manages to make the situation worse: her Brexit proposals get rejected 3 times and the party loses their majority in general elections, forcing them to reinforce their suicide pact with the fringe Brexit parties. In the meantime she puts in motion all the legal arrangements that make Brexit inevitable, and gets rewarded by being forced to resign in favor of the more extreme, pro Brexit side of the party.
-Finally a new openly pro Brexit PM arrives, and even though the UK is halfway through the deadline to make Brexit work, he decides to go all out on no deal, aggressively refusing to do anything similar to a somewhat organized transition process and therefore losing the good faith of his counterparts in the negotiation and the trust of the international community. Nevertheless, these actions are interpreted internally as the ones of a strong leader fighting for his country, and he wins the elections in a landslide paving the way for a chaotic no deal Brexit.
-Prior to the elections, the opposition got a window of opportunity (graciously handed by the new PM's ineptitude in trying to close the parlament) of getting together, get the ruling party out and starting to dismantle the Brexit process or at least to mitigate the most damaging parts of it. They failed miserably in the first task, the "get together" one, and therefore secured their place in history as accomplices by incompetence.
-Less than one month before the deadline and after selling for years the idea of a no deal the PM shows a surprise eleventh hour deal, with shortcomings instantly visible to anyone willing to read it. Anyway, that doesn't stop the PM from exaggerately praising the deal and calling Brexit complete (the Brexit minister position surprisingly keeps existing though).
-Approximately 6 months into Brexit, when the damage done has become pretty clear, the PM and his staff start reneging on the deal they just signed and congratulated themselves on, blaming the opposition in the process. He also threatened to break international agreements over the irish border, after failing to put protocols in place that everyone knew were neccesary 5 years ago. These issues have also halted any options of a quick deal with the US, making the problem even worse.
-10 months after Brexit the current PM has nowhere to go (except for continuing escalating the conflict with his main partners), the 2 previous ones are MIA (one wrote a book I think) and the fringe party that started it all has returned to his usual irrelevant place in UK elections. The ruling party looks comfortable though.