The article you linked makes it clear why L2 was chosen - this orbit allows continuous communication between Earth and the lander. If the satellite was at L2,

The article you linked makes it clear why L2 was chosen - this orbit allows continuous communication between Earth and the lander. If the satellite was at L2, this would not be the case, as the moon would be in the way, so it has to be far enough away to see both the lander location and Earth at the same time Also, orbiting the moon would give you coverage much less than half the time, and you’d need to track the satellite across the sky from the lander