In heavy seas you get water ingress into the raft. That can vary from a few millimeters to completely flooded. Also the raft will chill to ambient temperature. Not a good situation, even in ideal situations. The blunt truth of the matter is that liferafts are only intended to provide short term sanctuary for a few hours to a few days depending on the conditions.
Long term survival in a raft only occurs in tropical waters under unusual conditions.

It appears that in this instance the Crew had no chance to abandon. That strongly suggests to me that they were taken by a wave.