TPF started picking fights with other NPO allies (NSO, NG, AZTEC) about a year and a half before the treaty was cancelled. On top of their government slowly going inactive, feeling they had veto power over NPO's FA, and consistently voicing support for wars against said NPO allies, TPF decided to sign an MD-level treaty with MI6. It was common knowledge that MI6 and NPO were on bad terms with one another at the time and that there was likely to be a war between MI6 and NPO+allies. So NPO felt justified cancelling the treaty, especially after its initial reactions to TPF's behavior were conciliatory (NPO cancelled its NSO treaty a year before it cancelled its treaty with TPF).
Otherwise your accounting is correct - NPO and allies hit TPF preemptively after declaring war on MI6. And yes, it was a mess.