The person asks how Porre got strong enough to overthrow Guardia, and even mentioned it in his question, and Kato acknowledged it and vaguly answered it.
Apparently unlike Porre, Truce is a village, not a country. Truce is a village of Guardia. I'll break down the video as how I understand it. It starts off talking about the Fall of Guardia. Its the inside of Guardia Castle, as the Guardia Crest is on the back wall. Shadowed Figure 1 kills Shadowed Figure 2. Porre Flag flashed. We then go to the Masamune disappearing. Village burning, people dead. "Good" Masamune in blood. This basically explains how the Masamune turned evil: kill all those people. And it somehow ties it to Porre, being in the same video that has the fall of Guardia.
After the invasion, Porre does eventually have contact and dealings with Lynx. People assume Lynx had something to do with the fall, but thats not so. Serge's father was even corrupted by FATE untill 1006 (a year after the Fall), and he didn't fully turn into Lynx till 1010, I think. So impossible for Lynx to have had something to do with it.
I have always guessed that unanswered questions on Guardia's fall were to be answered in the next Chrono game.
