That would be about a half hour into Kerry's tour of duty
While some credit Kerry's connections, and others credit some sympathetic bureaucrat, it may be that some other officer realized quickly that Lt. Kerry was more risk than asset.
Kerry's proponents (from when they were in the same boat), likely took a liking to him because for them, as enlisted personnel, he presented as a non-conformist officer with whom they could discuss their concerns.
There are plenty good officers, conformist or non-conformist, who have the talent for talking with enlisted personnel.
What made Kerry different, was, is my guesstimate, that he was non-conformist on too many important matters regarding his duties, not just his views about the chain of command with which some enlisted people may have found sympathies.
For all of John Kerry's talk, his war record, his memories, do not match up with the kind of operational awareness, mindset, and preparedness that are required of an officer, good or indifferent. There is a certain level of getting your act together, getting with the program, that you must do, in order to face the enemy and have some chance of success.
The type of boat commanded by Lt. Kerry, to be used as he insists, would have had much attention to detail in order to insert S.E.A.L. or other special force operators. Yet no mention of officer responsibilities, by Kerry or his buddies; just talk of his heroics.
Spec. Ops folks are picky about loud engines and poor seamanship that might trip up the day or evening at the office.
For a spec. ops warrior and buddies, to be prepared in detail for a mission, but to then board Lt. Kerry's boat and find it a homing beacon for communist ears, does not fit with the Lt. Kerry whose few military supporters "know and love" for his disrespecting the basic job requirements.
Which trait, you have probably guessed correctly, was evident from the start.