Fear serves as the impetus of almost all the action in this play, as we can see from the very beginning. Abigail knows that she is in danger of severe punishment and possibly death if her behavior in the woods becomes known (she has been dancing naked and drinking blood).
This reasonable fear leads Abigail to begin to spread her lies about witchcraft, deflecting blame and attention from herself.
Fear is the driving force in Puritan Salem in 1692, and it is the driving force in this play, as well. The Puritan culture left little room for forgiveness of sin' so, if sin wasn't exposed one could believe it didn't exist. Pointing out the sins of others was driven by fears that one's own sins would be exposed. The girls are afraid of getting in trouble so they "cry witch." This religious community is afraid of witchcraft (as it was a sign of Satan and his work), so they believe the flimsy evidence of these emotional girls. In a community where people wanted what others had (such as land), the trials became an opportunity to capitalize on the confusion by accusing others of vague or imaginary crimes. Fear is, indeed, the source of conflict in this play.
Fear is a very basic and common human emotion and is the basis for much of the characters' actions and reactions in Arthur Miller's play. It is certainly a source of conflict in Salem in 1692, as peoples' fears of witchcraft and the unknown, of the Puritan authority, and of death itself all led to a vicious circle of accusation and conviction.
Other factors caused conflict on their own or intensified peoples' fears, including lust and jealousy, pride, and revenge.
I think that this makes some sense in the context of this play. Much of the conflict in this play occurs because the population of Salem is afraid. They are afraid of things they do not understand. When things happen (like Betty going into the coma) they become afraid.
However, it is not sufficient to say that fear is the only cause of conflict. You have some people (Putnam) who are trying to use the fear to advance their economic interests. When they do this, they make more conflict. This is conflict that does not come from fear.