With the story coming out about the fertilizer I wonder know if the TAPT was just the trigger device.
I wondered about that, too. Can TATP be used that way? The articles have said that he was not successful in buying the fertilizer, but perhaps there was somebody else who was successful and they were planning on putting these triggers on larger explosive devices that they had already put in place (although it says the stadium had been swept for bombs, so presumably anything larger would have been found).
Hinrich didn't get the fertilizer he was seeking. I suspect that the original plan was ANFO bombs (Ammonium Nitrate/Fuel Oil) the type used in the first WTC attack, and the Murrah building bombings. This was apparently scrapped in favor of TATP, the components for which are easier to obtain at present...
the infowarrior