That’s most usable explosives from my limited understanding. A small primary explosive charge setting off a more stable bulk explosive, whether that be ANFO or C4 or something else.
He may have already had dynamite, but not a Uhaul full of dynamite. Which would have been difficult and quite dangerous I imagine.
The same losers come by gun stores and ask how to convert their AR-15s into machine guns. Actual police work is difficult I guess, so they go on these fishing expeditions.
Their geriatric audience still makes the connection between drugs like that and the unpatriotic, godless hippie movement.