Well, the only thing we have to go on is the linked story. Based on that:

"At first light on Jan. 15, they peeked outside only to realize visibility wasn’t any better.

They thought they were in the Edith Creek basin and that following it would lead them close to the Paradise parking lot.

They were actually in the Stevens Creek canyon, which descends farther east of Paradise to the Stevens Canyon Road, which was closed for the winter.

Unaware of the mistake, they kept going."

So on the 2nd day, they started out at first light. But by (apparently) not having a paper map, and not using their GPS to give point position on said map, they were in gross landnav error. This error is what caused them to need to shelter for the 2nd night. It also looks like he hadn't recorded a waypoint at their car. If he had that waypoint, just with the GPS he would know the straightline distance and direction to the right parking lot.

Woulda/coulda/shoulda, I know, but when a guy intentionally goes in with a GPS and no map (especially around Rainier in winter) then can't leverage his GPS without its electronic map, it's a landnav fail.