Just my opinion, but I think many factors come into play here that may distinguish between grooming, or instead a healthy Sunday school teacher relationship.
Was Mica just one more kid in his class? Or did he pay her extra attention, did he ask her to wait after class without others around? Did he buy her things? Did he tell her to keep anything secret? Did he talk to her only about the Bible or did he tell her inappropriate things, like how pretty she was?
Clearly she caught his eye later when she was also married, but we don’t know when that seed was planted.
Maybe her family knows the answers.
I taught 8th grade for 25 years, so most of my adult life was spent with 13 and 14-year olds, and the occasional 15-year old.
Kids used to ask me to attend their basketball games after school, or softball games, or various other activities.
I would not do that unless I had a note from their parents saying that they wanted me to do so, and I’d rather sit with the parents when I was cheering for them.
Even in school, if we needed to talk to a student privately, we kept our door open and if it was a major issue we would have the guidance counselor or assistant principal with us.
So I am judgmental when anyone with authority over children does not take steps to assure propriety.
IMO and IME.