Part of the ongoing Verse Quick Reference project.
Mar 1:16 And as He walked by the Sea of Galilee, He saw Simon and Andrew his brother casting a net into the sea; for they were fishermen.
This verse uses a grammatical construct similar to a classic verse used to argue for Calvinist election:
Joh 10:26 but you do not believe because you are not among my sheep.
Mark 1:16 is a lesson not to make too much out of prepositions. In Mark 1:16 the fishermen were fishing because they are fisherman. In John, Jesus’ listeners do not believe because they are not follows of Jesus. In Mark, the idea is not that someone is metaphysically forced to fish if they are a fisherman. Instead, the text is explaining why they are fishing: because they chose to be fisherman.
John 10:26 similarly can easily mean that people do not believe because they have chosen not to follow Jesus. Contextually, Jesus could easily be calling out people who are feigning belief.
The construct (something is true “because” of something else) does not necessarily mean the second thing “caused” the first or that the first inevitably leads from the second. Instead this construct is drawing a logical connection that may or may not be causative.