The far side is not always dark
From Earth we see mostly the same half of the Moon because its rotation is synchronised with its orbit. The far side also experiences day and night; it is not permanently dark.
Chang’e 4 came first
Chang’e 6 was not the first spacecraft to land on the far side. In 2019, Chang’e 4 and the Yutu 2 rover made the first landing there. Chang’e 6 returned samples from that region to Earth.
Studying the samples
The material can help scientists compare the Moon’s two sides and investigate the history of lunar impacts and volcanism.