I was thinking about this also.
If family went to check and they didn't notice anything (assuming they didn't find a large amount of blood somewhere or the entire house ransacked) then maybe it's smaller less obvious things that LE put together. All I saw mentioned was someone called family to say she wasn't at church and then family briefly searched and then called LE.
If she didn't take her cane or walker, didn't take her medication, didn't take her phone, etc. That would be suspicious, but I don't know if I'd say a crime must have been committed based only on those things.
What else could it have been? Was something left on in the house? Was the bed slept in Sat night? Were her pajamas missing? I am only thinking of my grandma, and she always wore a nightgown and a house coat with house slippers. Younger generations might not be so much into bed clothing being specific pjs or night gowns, but I feel older people do still wear gowns or things like that specifically for sleeping. When my grandma took those items off she hung them up on a hook on the back of her bedroom door.