Maybe a reflash of ECU or FICM?
Something similar just happened to me a few weeks ago. First the disclaimers, I have a 6.0 and not the 7.3, also my symptom was a no crank, no start.
Prior to this no crank symptom , I let the van sit for a few weeks and let the battery run down. Tried to start with a longish ~10 sec crank stopped and made second crank attempt hand slipped immediately after starter started spinning. Tried the ignition again and nothing.
Tested and replaced fuses for engine control electronics. Jumped the terminal on starter solenoid...cranked. Rotated all the relays around. Still no crank from the key. Jumped the starter relay terminals... cranked. Voltage to relay observed. Disassembled column to check ignition switch. Tried shifting while holding key to start to eliminate transmission position sensor. Nada. Pulled out my backup PCM and swapped it in. Cranked and started up without a hick-up.
Swapped my old PCM back in, got out my SCT tuner to attempt a flash or reprogram of the PCM. Incidentally had a tune on my PCM (Must of forgot to reprogram after getting back on road.
), so I had it returned to stock. Turned the key and it cranked, started and ran.
My guess, the quick let-off on the starter on the second attempt caused a power surge exacerbated by a low voltage condition that corrupted the PCM. Coincidentally I have a CTS2 and the whole time was operating normally receiving data and it did not report any unusual error codes.
Just throwing this out there as another possibility. Good luck.