it's probably worth noting that even the court whose verdict this overturned agreed with the basic premise that Trump engaged in conduct that constitutes an insurrection--their ruling was merely that, on a technicality, he did not qualify as an officer of the United States (a legal term with a specific, vague meaning in the Constitution). there really is not a dispute that what he did was unlawful conduct, only whether that carries the penalty in question (being unable to legally run for office in a number of states)

Prior to the election, Donald Trump incited the Proud Boys specifically and other militant groups to insurrection with his 'stand back and stand by' comments. These were taken by many observers and the Proud Boys themselves as calls to seditious conspiracy. Members of the Proud Boys then planned the 6 January attack, including planting bombs around Washington DC, and were involved in the attack on the Capitol. Many have been convicted of this conspiracy, so there's no legal question as to whether it happened. I don't know if incitement to an insurrection counts as insurrection in and of itself. It might do, but I'm not a lawyer.

Having lost the election, Trump knowingly engaged in a conspiracy to undermine a free and fair election, which he knew he had lost, in order to keep himself in power. Some aspects of that conspiracy have gone to trial and defendants have been found guilty. So, there remain some legal questions as to the extent of the conspiracy, but it is quite clear that people involved broke the law in the pursuit of the conspiracy. The conspiracy constitutes an attempted insurrection in itself.

When his conspiracy failed, he then incited a violent attempt to overthrow the election (the 'fiery stuff to a rally') and allowed it to continue as people were violently attacked. This also constitutes an attempted insurrection.

He gave aid and comfort to the insurrectionists by delaying sending in additional police, by calling them good people while they were beating cops to death, by targeting Mike Pence with his rhetoric while the capitol is being stormed, by telling them he loved them, by telling them he’ll pardon them if re-elected. This played out in real time, on TV and on Twitter. These facts are not in dispute by any objective observer.

Now re-read the 14th amendment. Might also be a good idea to read the Jan 6 Commission report.

Pretty fucking cut and dry.

I live in Australia, and even I saw what was happening in the buildup.

Months before he was already starting with rhetoric claiming the election was rigged and it was blatantly obvious he was planning to try to overthrow the election

Read Seth Abramson.