If they had to work for three hours to get the snow and frost off of a medium/large single, I’m thinking that the weather was ahead of them when they started, but maybe things changed.
500 OVC, snowing, and a temp/dew point match is par for the course in the upper Midwest this time of year. It can be an annoyance, or it can be deadly depending on the mitigating factors. I am assuming that a guy qualified to fly an airplane of this size/capability had the wherewithal to make an appropriate decision, and we are all not privy to whatever other information played into the matter.