It’s not just that we now also know that the president surrounded himself with criminals (some of whom, remember, were also undeclared foreign agents). Nor is it just that Michael Cohen says that Trump directed him to commit a felony. Indeed, if all that Trump had done was to have affairs and illegally pay hush money to cover it up, I’d argue that it wasn’t really even close to enough for impeachment. Worse than what Bill Clinton did, perhaps, in that Clinton merely lied about an affair, but Clinton never should have been impeached.
No, what has really moved the needle on this is Trump’s constant cheap gangster rhetoric and flat-out unwillingness to support the rule of law. For example, it was utterly inappropriate for the president of the United States to comment during Paul Manafort’s trial, including while the jury was out. It undermines the rule of law for the president to constantly run down the Department of Justice, buying into wild and discredited conspiracy theories about how everyone in the government is out to get him and his associates.