Why did he cut the branch he was sitting on?

In a unanimous decision by all 11 judges, the UK Supreme Court ruled yesterday that Boris Johnson acted improperly when he advised the Queen to prorogue parliament. "The decision to advise Her Majesty to prorogue Parliament was unlawful because it had the effect of frustrating or preventing the ability of Parliament to carry out its constitutional functions without reasonable justification," said Supreme Court president Lady Hale. Parliament was suspended on 9 September and was due to reopen on 14 October. Prime Minister Boris Johnson was accused of lying to the Queen to get her assent. Johnson is cutting short his visit to the United Nations in New York to fly back to the UK but speaking to journalists he was defiant.  "We in the UK will not be deterred from getting on with delivering on the will of the British people to come out of the EU on 31 October," he said. Earlier the highest civil court in Scotland ruled against Johnson saying, "This was an egregious case of a clear failure to comply with generally accepted standards of public behaviour of authorities." But the High Court in England and Wales found that Johnson had acted lawfully. The Supreme Court has settled that argument even though the government argued that the court should not interfere in the business of parliament. The court opined that it was stopping the executive from abusing its power to stop parliament from exercising its duty to question the government. After parliament voted to stop a no-deal Brexit and ordered the Prime Minister to seek a 3-month extension till the end of January 2020, Johnson said that he would rather be "dead in a ditch" than ask for an extension. That is the trouble with Johnson. He has adopted an aggressive attitude both against the European Union (EU) and the opposition in the House of Commons since the beginning, promising to leave the EU with or without a deal. He threatened EU negotiators with a no-deal Brexit if they did not surrender on the Irish backstop. The Irish backstop is a continuation of the customs union between the UK and the EU to avoid a hard border between Northern Ireland, a part of the UK, and the Republic of Ireland, a member of the Euro area. It is hated by Brexiteers because they see it as remaining a part of the EU, as the UK would still have to comply with EU trade rules. European Commission President Jean-Claude Juncker said that the backstop could be replaced if an alternative solution is proposed by the British government. However, Johnson has not provided any alternative, accusing the EU of being intransigent. Can Johnson defy parliament and refuse to ask for an extension and let Britain fall out of the EU without a deal on 31 October? He would then be in contempt of parliament and that would surely put an end to his political career. Johnson has US President Donald Trump's support but he cannot veto bills as Trump can. He has reduced his party number by expelling members who voted against him. He has cut the branch he was sitting on.