My money is on a remoaner who wishes to sabotage Britain’s relationship with the US in order to force Britain back into the embrace of the EU. There is a very large crossover between inveterate EUrophilia and anti-Americanism in the UK, and a similar crossover between pro-Ammericanism and anti-EU sentiment.
Or maybe he is a fall guy who worked with Brennan, et. al. to take down Trump. Darroch has been the Ambassador since 2016. The Brits wanted him out now before his role in the cabal became known. It will be interesting to learn if he had any contact with Steele.