Gents, I hope that you will pardon me for being somewhat controversial here, but didn't you just get what you deserved ?
During the covid crisis, Eurostar asked for help and the UK government turned them down, saying that Eurostar was not a UK company, did not provide any essential service, and therefore did not deserve any help. This view was shared by a large percentage of the UK public.
Is it not normal that in those conditions Eurostar decided to focus on EU needs first and let UK ones slip behind ? Nobody in France, Belgium, or the Netherlands is interested in traveling to Ashford or Ebbsfleet. London to Disneyland, the Alps, or the French riviera, is a pure UK market. All of that is way less profitable than the traffic between the four capitals because it requires lots of extra investment for very little return. Probably the 4 capitals market even subsidized the Disneyland and Kent ones. So, maybe not a pure retaliation act but don't expect them to go the extra mile for the UK market after having been treated like that...