A modicum of scientific inquiry and a smattering of awareness of the behavior of various explosives applied to the official fairytale says: fertilizer bomb placed in a truck on the street cannot accomplish the observed effects.
There’s also a substantial volume of eyewitness testimony, together with the usual news reports issued before the narrative was locked down.
There’s no excuse for not knowing; as with 9/11. But if you haven’t done the homework, this is a place where you’d be advised to stfu and not parade your ignorance.