I don’t think that’s the way to explain it. Roberts is doing his job. He’s got to champion the notion of an independent judiciary. But Trump is correct that the judiciary is acting in a partisan fashion. At a minimum that is the perception. And it did not start with Trump. The moniker Ninth Circus has been around since at least the Seventies. If the Dems are going to politicize the courts then they are not in a good position to complain that Trump calls them on it.
Roberts felt the need to defend the judiciary. He did a pi$$-poor job.