The UK were in because of their EU membership. No one could have taken that from them besides they themselves.
And once you are out you get treated like any 3rd party state. If you want a special deal you better bring some time and be prepared to start fresh.
The desire "to get Brexit done" in a very tight timeframe, pushed by populist politicians, did not allow for that.
The whole deal of the EU is to make cooperation between countries easier and to act as a single voice.
The UK reaps what they sowed