Shais Taub recently discussed this in an online presentation, and his take seemed to be (if I understood him correctly, I might be wrong about this) that OTD doesn’t happen in a bubble and all the cases he’s seen were caused by some sort of trauma, not necessarily the classic/literal abuse.
This. Because every individual is unique, there are people that experience very "light" forms of abuse in a incredibly traumatic fashion. It's all about the trauma, not the particulars of what caused it. Abuse is definitely up there, but I believe trauma and undealt with pain is the underlying cause of most people leaving Judaism.
On the topic of mental illness being disclosed- its disturbing to hear blanket statements either way, every case can be so different... I agree there are people who cover up things in a negligent or borderline malicious way, but I do feel that most peoplle are trying to toe the fine line of being honest but not laying themselves and their children victim to peoples unjust stigmas and prejudice.
I haven't formed an opinion about the "best" way of dating. I see much merit and peril in both the Chasidish and regular dating methods.
I do think the picture debate is a little overblown. But if it's being done definitely bit ways. It's sad these things go around and it's sad people automatically think that if it's going around its kit being done respectfully and responsibly.