Complex sentence: Despite initial skepticism, the first Hanse Sail turned out to be a great succes, mainly due to enthusiasm sparked by the German reunification, the sea border was open for the first time in decades.
Split into simpler sentences: Despite initial skepticism, the first Hanse Sail turned out to be a great succes. This might have been mainly due to enthusiasm sparked by the German reunification, as the sea border was open for the first time in decades.