Ahh Tough One!
From a scientific guess, I am going with the Coxsackievirus. This seems to be the one that is backed up with the most data. But still nowhere near enough!
Personally, I believe a major Trauma / Stress Event caused it.
Other notable mentions from me is Kenalog ( Immunosuppression Hayfever Injection I had ) or Covid ( Diagnosed April 2020 ).
One thing that stuck out to me, was that when I was in a honeymoon period and still had antibodies, I was repeatadly getting mouth infections every month. Once my pancreas packed up and I returned to back to insulin again this year, I never had one since. Ironically, I remember having a bad one in March 2020 last year aswell, before I went into Hospital close to DKA on diagnosis...
Still, this is our great unanswered question. Who knows
