It was common all over Europe for really old observatories to build in a new site, fortunately the old observatory was not torn down has happened in many cases.
Then as the utility of the new sites also waned, the old site was revitalized.
This happened similarly in England, where the Greenwich Observatory was moved to a new site in Sussex with new buildings, but then back to the old site again.
One issue was the increased crowding in the cities, and also astronomy was growing more focused on data from space in the late 20th century.

In any case the 40-inch (102 cm) reflector was one of the larger telescopes in the whole world for 1931, and is still a large and popular telescopes size even in the 21st century.
It was common all over Europe for really old observatories to build in a new site, fortunately the old observatory was not torn down has happened in many cases. Then as the utility of the new sites also waned, the old site was revitalized. This happened similarly in England, where the Greenwich Observatory was moved to a new site in Sussex with new buildings, but then back to the old site again. One issue was the increased crowding in the cities, and also astronomy was growing more focused on data from space in the late 20th century.
In any case the 40-inch (102 cm) reflector was one of the larger telescopes in the whole world for 1931, and is still a large and popular telescopes size even in the 21st century.
Stockholm Observatory