Allow me to summarise
Of
course, the SIS way 
In short, the whole thing about satan is a show performed to push
people into believing in god. Satan, much like TCS stars, r cast as
"baddies" because they r absolutely important to make the show more
interesting. Without satan, a lot of bad things tat happened cannot
be explained. Without satan, there is no scapegoat tat take up all
the blame like sickness and evil etc. Without satan, god cannot
bring fear to the people and they wouldn't come to him. Without
satan, tat is no role model tat warn people wat happened to them
after judgement. Therefore satan is actually god most favourite
angle because it makes god look better. In reality, they r actually
in cahoot with each other. God is more evil than satan because he
wanna act good yet in reality, performed all the evil things and
push all the blame to satan. Satan is really just an obedient
servent. No wonder he still acts as such even though he know he
will be "judged" at the end.
If u ask me, satan is prominent in almost all religion. Because he
is an essential ingredient for brainwashing and limit thinking. He
bring fear to people who will then act in extreme manners. Satan is
supposed to be so evil, so powerful tat the only protection men can
get is from god. He is also something like the "bad" parent tat
work with god (good parent) so tat people will view god as a
shelter from the "bad" parent.