IMO though, Johnson got his real mandate when he won the 2019 election. He 'Got Brexit Done'. For the TrueBelievers that was enough. Any old deal was good enough. Even though his deal was worse that May's, even though he put a border down the Irish Sea, even though he negotiated in bad faith. This was still predominantly an English victory.
Now that they are finding that any old deal isn't actually all that good, it's everyone else's fault.