"The way I understood it from the NTSB briefing video was:
1) the first officer noticed drifting off track when passing 90...93 knots.
2) runway track marks indicate a skid began at 1900 feet from threshold.
....and 3) Plane travelled another 700 feet before actually departing the runway.
"Why was runway 25 or 26 not used since the winds were more favorable from the west?"
As I mentioned prviously, I heard at least one other plane request 26 for LANDING as I was pax on inbound United flight to KDEN. (and it was approved by ATC)
To depart on 26, however, requires about a 3-mile taxi north and east into the prairie, whereas 34 L/R begin adjacent to the terminal with only about a 300-yd taxi.
Departing runway 25 is a shorter taxi, but requires taking off UNDER traffic inbound for 34 L/R.
Since most here, and presumably the 1404 pilots, thought the winds were within the capabilities of a 737, I guess it didn't seem worth the time.