Complex sentence: When it returned to Kraków in 1885, it was temporarily exhibited in the Sukiennice Museum because the Royal Wawel Castle was occupied at that time by the Austrian army, as Kraków was part of the Austrian partition of Poland.
Split into simpler sentences: When it returned to Kraków in 1885 it was temporarily exhibited in the Sukiennice Museum. This was because the Royal Wawel Castle was occupied at that time by the Austrian army as Kraków was part of the Austrian partition of Poland.