You might find it helpful to look at this ethnography of an EA group. Also relevant is this analysis of the Big Five personality traits of respondents to the Rethink Charity community survey. It has statistical flaws, but one takeaway is that most EAs are high in openness. Finally, there’s this Global Optimum Podcast episode on the personality of EAs.
Justification and signalling explanations don’t seem especially compelling to me because in some sense, everything is justification and signaling. Also, I’m not sure if you’re hinting at this, but it’s unlikely that you’ll be diagnosed with a mental illness just for being drawn to / believing in EA, unless it significantly impedes your everyday functioning. Since I’m not a therapist, I don’t think I can comment further on what a therapist would say.