Because of this is ambiguous. It may be either consequential as Good News Translation has it (Phillips “as a consequence of this”) or temporal (most translations “after this”; New English Bible “from that time on”).

Followers is literally “disciples.” Here the larger group is contrasted with the twelve mentioned in the following verse. For this reason Good News Translation has followers in this verse and renders “the twelve” of the following verse as the twelve disciples, thus retaining the more specialized term “disciples” as a reference to the twelve.

Turned back is translated in various ways. Moffatt and Revised Standard Version translate “drew back,” while Phillips and New English Bible have “withdrew.” Jerusalem Bible has “left him” and New American Bible “broke away.” It may be a Hebrew idiom, as is the expression (would not) go with, which is translated “no longer went about with him” by New English Bible and “stopped going with him” by Jerusalem Bible. Phillips translates “no longer followed him.” Moffatt (“would not associate with him any longer”) and New American Bible (“would not remain in his company any longer”) seem to have a wrong focus. The two expressions are essentially synonymous; one is used to reinforce the other.

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on the Gospel of John. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .