All they needed to do was copy the indictment from Trump’s impeachment trial, on which 57 senators voted to convict. A jury would have returned a conviction in five minutes.

He wasn't impeached for sedition. He was charged for inciting rebellion. Different claim.

Here's the text of that statute:

Whoever incites, sets on foot, assists, or engages in any rebellion or insurrection against the authority of the United States or the laws thereof, or gives aid or comfort thereto, shall be fined under this title or imprisoned not more than ten years, or both; and shall be incapable of holding any office under the United States.

law.cornell.edu: 18 U.S. Code § 2383 - Rebellion or insurrection | U.S. Code | US Law

This would certainly fail in court, because prosecutors would be unable to get around the limits on when speech can be criminalized. Under Brandenburg v. Ohio, there's a pretty significant limit to what speech the government can criminalize based on its effects. You have to be able to prove specific intent to cause imminent violent action, and that's actually quite hard to do if the person has not specifically used the words to direct a crowd to do a specific violent thing. It's much harder to prove up incitement or meet the Brandenburg test for public speeches than it to establish a conspiracy, where the core element isn't the speech but the agreement or common plan of action.

While Trump's speech had some martial rhetoric and generic calls to action, he never explicitly told the crowd to do anything violent or illegal. That's not incitement - and to the extend that "sets on foot" or "assists" are vaguer terms, a judge isn't going to let those be construed any more broadly than the Brandenburg test requires. Which is why he wasn't brought up on ordinary incitement charges under the DC Code, either.

code.dccouncil.gov: § 22–1322. Rioting or inciting to riot.