They have to worship Satan because God won't accept their empty offerings.
Chap 76 Book of the cave of treasures
5 Then God looked upon Abel and accepted his offering. And God was
more pleased with Abel than with his offering, because of his good heart
and pure body. There was no trace of guile in him.
6 Then they came down from the altar, and went to the cave in which
they dwelt. But Abel, by reason of his joy at having made his offering,
repeated it three times a week, after the example of his father Adam.
7 But as to Cain, he took no pleasure in offering; but after much anger on
his father's part, he offered up his gift once; and when he did offer up, his
eye was on the offering he made, and he took the smallest of his sheep
for an offering, and his eye was again on it. '
8 Therefore God did not accept his offering, because his heart was full of
murderous thoughts.