That is one bad trip! Glad everyone is ok, though.
We have season tickets to the Washington State University Cougar football games so have taken various trailers to eastern WA many, many times. Snoqualmie is a major mountain pass and lots can go wrong. We never had a problem pulling the trailer over the pass, but have plenty of troubles with cars through the years--in good weather and bad.
Hopefully, your next trip over the pass will be totally uneventful!
Cheri