It’s probably Republicans behind these Roy Moore rumors.
Notice how quickly McConnell and McCain and Flake et al came out demanding that he step down?
The GOP Establishment hates Moore. This is their attempted hit.
Just like with regards to Trump they would rather lose the seat than risk having it taken by an outsider whom they can’t control.
The republicans floated these rumors to Trump before the primary, which is probably the reason Trump at the time endorsed Luther Strange.