1. notice that CNN and WP report these incidents as 'collapses', as if that happened for no reason at all. AP News even goes so far as to say the Bridge Collapse caused the train to derail. < They trace causation to the collapse.

Then, 24 hrs later it's "officials say" that there were explosions.

2. C4 has a signature, and they need only one gramme to identify it. https://pubmed.ncbi.nlm.nih.gov/20229010/#:~:text=Cyclohexanone%20and%20DMNB%20are%20associated,fiber%20followed%20by%20IMS%20detection.