Looks like the plane got airborne in ground effect, but had trouble gaining altitude. My first thought is that it was overloaded.
The Stinson 108-3 has an empty weight of 1,300 pounds, a gross weight of 2,400 pounds, and carries 50 gallons of fuel. So they had 1,100 pounds to play with, minus 300 pounds of fuel if they had full tanks; 800 pounds left for the pilot, passengers, and baggage. The passengers didn’t look that hefty, so I’m guessing they weren’t over-gross.
But it looked like high country, and it might have been a bit warm. Density altitude may have been rather high, so they aircraft might have been too heavy for the conditions. This is armchair post-crash analysis, of course. I’d be interested in reading the NTSB report when it comes out.
After reading the article:
Yeah. Warm day, high altitude, possible mountain wind conditions.