Basically what he is saying in video for what I understand. If Mohammed fateh (may Allah keep him safe in grave and offer him paradise) bought the Church then there is no problem with that.
However if the church was forcefully converted to mosque without Christian consent than that is not allowed in Islam. Whether it be conquered or on terms it is not allowed.
There are much more issues he has raised as well in video.
Basically it Seems his views on this issue is similar too Ghamdi Saab.
My own opinion it should have stayed a museum, however if forced than if Islam permits given back to the Christians.
Allah knows best