v. 6 — Shock at rapid desertion
Paul says he is “astonished” () that they are so quickly deserting the one who called them and turning “to a different” () . The move is described relationally (desertion), not merely as a change of opinion.
v. 7 — No true alternative; only disruption
He immediately qualifies the statement: it is not that there is a legitimate “other” gospel. Rather, “some” are troubling the communities and intend to alter the message centered on Christ ().
vv. 6–7 — The passage’s logic
A quick turn is interpreted as desertion, the “different” message is exposed as illegitimate, and the practical cause is identified as agitators producing unrest and reshaping what the communities had received.