I don’t think Osteen’s church was flooded. But the area around his church had a lot of flooding, and it was probably difficult to get to his church. For him to open his church, people who are employed as church administrators, and church volunteers, need to be present and organize the effort. For a church the size of Osteen’s, many of his key people probably live several miles from the church, and it would be very hard for them to get to the church.
In the area around where I live, several churches have opened their doors to people who had to evacuate their homes. No mosques in my area have done this. Maybe they have done this for their members, in which case I wouldn’t know about it, but not for the general public.
I am a member of a Nextdoor web site for my neighborhood, and refuge locations for evacuees are posted there for our part of town. No mosques have been listed. Maybe somewhere else in Houston, mosques are opened for this purpose, but not in my area.
They showed pics of flooding in the church.