It's not possible to climb certain routes on Mt. Hood UNLESS it is ice/snow covered. This is because there is too much scree (small, loose rock). The men were training for Everest. Climbing Hood in the spring would not approximate conditions to be found on Everest. They wanted a REALLY tough climb in severe coditions to test their mettle.
They allowed themselves extra time to complete the climb, but someting happened to one of the climbers--not known what--and he could not continue. The other two built a snow cave and left him there, going on to get help. During the period of delay, bad weather moved in, stranding them all.
.....It was ludicrous for them not to wait until at least late spring......
Check your calender. Winter doesn't start for two weeks after their expedition. In fact, their trip is being accomplished in late Fall.
If you educate yourself about Mt. Hood, and climbing it, you will learn that when the snow melts, or is melting is the most dangerous time. There are rock slides, and showers of ice pellets and rocks. I am not a climber, but have been reading about it. The snow bridges over the crevices also melt.....