Indeed, both Kunst, künstlich, künstlerisch share their etymology from Kunst that was already present in Old High German in the meaning of knowledge (Kenntnis) and skill (Können).
It was until in the 18th Century when künstlich was indeed used in the meaning of being artfully made or from a technical high level:
Der Apfel war aber so künstlich gemacht, daß der rote Backen allein vergiftet war.Schneewittchen
Only later there was a shift in meaning for something that was unnatural, and to an exaggerated extend man made. Then – like in English – the meaning of künstlich became artificial and most of the original meanings got lost.
This was not the fate of künstlerisch (artistic), an adjective that only came up much later in the 18th Century for something that was created by an artist. Similarly the adjective kunstvoll (artful) maintained its connection to art until today and it now replaces künstlich in its pristine meaning.