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@MatthewHartke often promotes cognitive dissonance theory as an explanation for the rise of early Christianity. So I read a piece he recommended entitled “The Process of Jesus’ Deification and Cognitive Dissonance Theory” by F. Bermejo-Rubio. See my thoughts below. https://twitter.com/MatthewHartke/status/1258830376241225728
A little background... The grandfather of cognitive dissonance theory was Leon Festinger. Unfortunately, his “groundbreaking” study of cognitive dissonance in a flying saucer cult turned out to be an extreme example of the observer effect and a methodological disaster.
The sociologists who infiltrated the group prompted cult members to act in ways that would confirm the hypothesis of the researchers. At one important cult meeting, 1/3 of the attendees were sociologists. A sociologist even led one of the meetings! It was a methodological mess.
Bermejo-Rubio rightly acknowledges this early setback for cognitive dissonance theory, but then proceeds to appeal to Festinger’s conclusions throughout. One can only wonder whether he experienced some cognitive dissonance of his own while writing this piece?
Footnote #18 on p. 126 encapsulates some of the problems with this paper... 
In this footnote, with a simple wave of the hand, Bermejo-Rubio summarily dismisses NT Wright’s objection regarding the application of cognitive dissonance theory to the early Jesus movement.
He states (without evidence) that Wright’s objection is “dictated by theological prejudices and fears.” and “Theologically-minded authors, tend to rule out anything questioning the complete uniqueness of the movement they belong to.” Bigotry in the guise of critical scholarship?
He doesn’t actually engage Wright’s objection to CDT as an explanation for the rise of early Christianity, avoiding it altogether. If you don’t address the challenges of your position’s most strident critics, then you inadvertently reveal the frailty of your argument. 
Footnote #18: “CDT stresses recurrent patterns and similarities which tend to reappear time and again” If true, we should see similarities in the behavior of adherents of other 1st century Jewish messianic groups following the execution of their leader. Spoiler alert... We don’t.
On pp. 135-6 Bermejo-Rubio again cites Festinger’s conclusions stating, “dissonance can be reduced by adding new cognitive elements consonant with the belief system.“
Did you catch that? “Consonant with the belief system” A special resurrection prior to the general resurrection at the end of the world wasn’t “consonant” with the beliefs of 1st century Judaism.
Footnote #48 on p. 136, Festinger is again quoted: “In the presence of dissonance, one would expect active seeking out of information that would produce new cognition consonant with existing cognitions and the avoidance of information that would add to the dissonance”
If anything, the claim that Jesus had been raised from the dead in a special resurrection prior to the general resurrection AND now needed to be included as part of who God is, all in a monotheistic 1st century Jewish world, would only greatly increase the dissonance.
Bermejo-Rubio conflates the literary diversity within Second Temple Judaism with a theologically pluralistic society.
Yes 1st century Jews conceived of spiritual entities other than Yahweh, but only Yahweh was worthy of worship. The worship of Jesus in such an environment would only increase dissonance, not reduce it.
See Larry Hurtado in How on Earth did Jesus Become a God? 25-26.
Bermejo-Rubio says expanding the gospel message to include Gentiles was simply another means of reducing dissonance Jesus followers felt: “the extension of salvation to Gentiles could be a function of the need to attain wider social reinforcement through mass proselytism” (142)
Although acknowledging Paul’s role in initiating the mission to spread the gospel to the Gentiles (Gal 1-2), Bermejo-Rubio misses a serious problem. Paul wasn’t part of the initial Jesus movement.
Paul would have no need to reduce dissonance. In his pre-Damascus Road outlook, a messianic pretender had justly been exposed as a fraud. Plus, Paul’s outreach to the Gentiles wasn’t always embraced by the initial Jewish followers of Jesus.
CDT has been refined since the days of Festinger and can provide insights into human behavior, however, it is a theory that *still* suffers from serious methodological flaws. I would recommend this critical analysis of CDT conducted by Vaidis & Bran. https://doi.org/10.3389/fpsyg.2019.01189
The attempt to draw conclusions based on the psychology of figures attested in ancient literature is ultimately a fruitless endeavor. We simply don’t have enough access to their individual backgrounds, motivations, thought-patterns, to form any sort of accurate assessment.
In trying to assess the psychology of historical figures from the 1st century we end up projecting our own modern sociological dynamics onto a world that wouldn’t recognize them, thus committing one of the most grievous of historical sins...anachronism.
I appreciate @MatthewHartke recommending Fernando Bermejo-Rubio‘s work. I went on to read "Was the Hypothetical Vorlage of the Testimonium Flavianum a 'Neutral' Text?“ which I thought was an excellent piece. I look forward to reading more! https://www.academia.edu/8139663/_Was_the_Hypothetical_Vorlage_of_the_Testimonium_Flavianum_a_Neutral_Text_Challenging_the_Common_Wisdom_on_Antiquitates_Judaicae_18.63-64_Journal_for_the_Study_of_Judaism_45_2014_326-365
