In ten years as a Christian school teacher I learned something: most Christian school teachers, including me, don't have a lot of ability. Most of them couldn't pastor a church if their lives depended on it. But I also saw that many of them served God diligently, and that He blessed them with success.
Occasionally, a Christian school teacher with little ability would start a successful ministry within a church. There usually was not a problem from Christians with more ability, but from Christians who THOUGHT they had more ability. A Godly and successful saint would suddenly find himself being attacked by an envious church member who demanded control of the successful ministry. Seeing the weakness of the low-ability Christian, an envious person could often rally others against him and steal the successful ministry.
Most first-time missionaries are Christians with little ability. They have rarely served in any high position in church. If they succeed on the mission field, they will have a hard time protecting themselves from envious co-workers.