This fits with my general knowledge of how such things work. TLDR: Those with the most skin in the game were the most likely to try to save face and double-down on their stated beliefs. Those who had lost less had an easier time going "Whoops! I was wrong!" and getting on with their lives:
Some of the believers took significant actions that indicated a high degree of commitment to the prophecy. Some left or lost their jobs, neglected or ended their studies, ended relationships and friendships with non-believers, gave away money and / or disposed of possessions to prepare for their departure on a flying saucer, which they believed would rescue them and others in advance of the flood.
As anticipated by the research team, the prophesied date passed with no sign of the predicted flood, causing a dissonance between the group's commitment to the prophecy and the unfolding reality. Different members of the group reacted in different ways. Many of those with the highest levels of belief, commitment and social support became more committed to their beliefs, began to court publicity in a way they had not before, and developed various rationalisations for the absence of the flood. Some others, with less prior conviction and commitment, and / or less access to ongoing group support, were less able to sustain or increase their previous levels of belief and involvement, and several left the group.
This is not inconsistent with what we know about the process by which people are radicalized and become members of extremist political groups and the like. Part of the process is that it becomes increasingly difficult to get respect, make meaningful social contacts etc with people outside the group. Once you pass some point of extremism, outsiders become openly hostile and their reactions give you no good path back from your position.
Being seen as "crazy" or "wrong" or "stupid" is too much to bear. Better to reject the entire world -- knowing it won't be nice to you at this point -- than to admit "Okay, maybe that wasn't the most rational thing to do."