And it is easier to see the "visual references" at night. So you have a greater chance than during daylight hours in very marginal conditions.
It is an interesting simulator exercise reducing the touchdown RVR by say 25m at a time starting at 550m. CAT 1.
Commence the approach from 3nm with full approach lighting down to DA.
A competent crew can safely land above 400m.
Below 400m is not really viable using CAT1 DA limits.
As to why 1100m was specified as RVR minima when inbound?
Perhaps the ac had failed equipment, and this is what was required for a non precision approach? Speculation on my part.