So it turns out that Robert Mueller isn't a TV star after all.

Maybe the former special counsel was never going to wow America in his congressional testimony by unveiling new information or perspectives about President Trump's links with Russia. Indeed, Mueller made it clear months ago that the report he submitted to the Department of Justice was his complete statement on the subject. But the president's critics held out hope that the politics surrounding the inquiry might change if Americans could just hear the results of the investigation straight from the prosecutor's mouth — they just needed to present the public with an unfiltered, credible talking head to counter Trump's constant "no collusion, no obstruction" refrain.

On that count, the early consensus is that Mueller's hearings failed. And for that, I blame former FBI Director James Comey.

If Comey had kept his mouth shut on several occasions in 2016, there is a chance that Mueller would have been more willing to make a bold statement during his testimony. Instead, Americans were treated to a master class in avoidance and side-stepping.

You will recall that Comey's fall from grace began in July 2016 — right in the middle of the hotly-contested presidential race between Trump and Hillary Clinton. The FBI had been investigating Clinton's use of private email servers while she served as secretary of state, and Republicans were continuing to use that investigation against Clinton on the campaign trail. So when the investigation ended, Comey made an unusual decision: He decided to recommend against prosecuting Clinton. And he decided to explain why.

Prosecutors almost never do that, as Comey admitted during his announcement. "I am going to include more detail about our process than I ordinarily would," he said, "because I think the American people deserve those details in a case of intense public interest." He then announced the FBI wasn't recommending charges — but he also slammed Clinton as "extremely careless" in her handling of classified information.

The decision left both Democrats and Republicans angry, albeit for different reasons. A Department of Justice investigation would later criticize Comey, saying he "violated long-standing Department practice and protocol by, among other things, criticizing Clinton's uncharged conduct." Then, somehow, Comey made everything worse. Less than two weeks before the election, he notified Congress that he had reopened the email investigation, disregarding concerns he would sway the election.

No charges ever came from the additional investigation. But Clinton blamed Comey for spoiling her chance at the presidency. Comey later said he would have done some things differently. And when Trump wanted to short-circuit the growing Russia investigation in 2017, Comey's unorthodox behavior in handling the email case provided a handy if temporary — excuse.

Comey has lived with some disgrace ever since. But he might deserve more sympathy than he gets. His letter to Congress was meant, in part, to protect Clinton's presidency from being perceived as illegitimate if news of the reopened investigation got out after she won the election. History didn't work out that way, but even the later Department of Justice internal investigation admitted Comey faced "unattractive choices" on his way to making a "serious error in judgment."

It's possible that some of this was in the back of Mueller's mind. Democrats needed Mueller to confidently explain his charging decisions in a clear fashion that even non-political, non-legal Americans could understand. They needed Mueller to abandon his usual silence and adopt just a little bit of Comey's over-transparency to make it work.

The lesson from Comey, though, is that there's little reward for transparency. In fact, over-sharing could ruin your career and turn the public against you. So Mueller stuck stubbornly to his famous stone-faced reticence, often declining to answer questions — or answering questions merely by affirming that his report contained the answers. A scintillating soundbite was hardly to be found. The audience was left wanting more.

This isn't about siding with "optics" in the great "optics versus substance" debate. The substance of the Mueller report — that the Russians interfered in the 2016 to help Trump, that Trump and his campaign welcomed that interference, and that Trump tried to short-circuit the resulting information — has been available for months now. The hearings were meant to translate that substance into optics. To make that happen, Democrats needed Mueller to say boldly and directly on camera what he'd said in the report, and to skip the double negatives along the way. That didn't happen.

None of this changes the bottom line: Trump is a bad president, a man who puts his own self-interest above the good of the nation, and has done so since the 2016 campaign. The Mueller report is far from the only evidence we have of that notion. Democrats must continue to pound that message home, whether through an impeachment inquiry, or during the 2020 election. It's become clear that they won't get Mueller to make the case for them.