Ever since Robert's first screwy ruling from the Supreme Court bench I have maintained that the behind the scenes movers and shakers of the Dem Party have got something damning to hold over his head as blackmail. It's not enough to actually destroy him -- or they would always be able to control him -- but it's just bad enough so that on occasion they can risk using it to pull him up short when it really matters to them.
Obviously I could be utterly wrong about this. But it seems to fit the weird pattern of his decision process.
But as to his rationale for not impeaching these obviously politically corrupt leftist judges for trying to BE the Chief Executive from their benches; 'That it's never been done before', doesn't hold water when you consider that prior to Trump, no president was ever repeatedly taken to court for four years after his presidency over garbage WHILE the Supreme Court watched and said and did absolutely . . . nothing to halt what was OBVIOUSLY judicially-generated persecution.
Or as you noted, Roberts was claiming a non-precedent as a precedent.
Caption this Meme