The Crash was a mysterious and catastrophic event which destroyed the worlds Nodes and leylines, effectively preventing magic-use and rendering magical devises unusable.
However, even after the Crash, there are still trickles of magic coming up, meaning that certain magical devises (robots for example) and locations, notably many of the Mansion features operate (but not all(
)) and many of Ludwig's inventions still function(). People with enough skill can still be magicians.
According to Olaf Larssen, at the time of the story magic is 2.42% stronger() than twenty years before and he expects a recovery.