@ Latte tester...
"I thought the max tailwind for landing a 601 was/is 10kts... Clearly reported wind at 16kts...with gusts"
You are correct... The aircraft's limitation in the AFM is max tailwind component of 10kts.
On their second approach prior to landing the tower gave them the wind as 320 at 16 kts with peak gust of 28 knots within the last minute.
Given the high TAS because of altitude, increased actual approach speed for turbulence/windshear correction, add to that a high rate of descent to get down from the MDA to the runway and a crew apparently flying into KASE for the first time in less than ideal conditions, the holes were lining up for a disaster to happen.
That Challenger must have been smoking into KASE. The G/S must have been very high!