My Dad spent some time on the Thresher but decided submarine duty was not for him. He always remembered those lost.
The theory I was told in sub school was immediate response to a reactor scram was closing the main steam stops. A seawater line located under the scram breakers failed at the Thresher’s test depth and sprayed seawater up into the reactor scram breakers causing them to trip, scraming the reactor. No steam for the main engines, major flooding, and a failure of the emergency blow valves. A slip below crush depth and goodbye. USS Scorpion was a totally different issue. Hot running skipper and Russians near the Azores. Fast Attack boats like to get close. Rumor was to close. MM1(SS). USS 640 Gold.