I really think it was a unique moment in time. You had networks with news departments that were staffed with actual journalists, because the news was a prestige loss-leader type of thing for the networks. It didn’t make them money directly, but it got them taken seriously with the public and advertisers. There were few other near-real-time (comparatively) news sources then. Radio was about it, as everything else was print. Television had immense social influence in an era when it was very hard to impossible for average folks to make the sort of video coverage we take for granted now.
More importantly though, to me it seems that back then, there was still a residual degree of trust in the essential goodness of the national character, and a faith that despite bad decisions and actions we were still on the side of the angels. The media went into the war in Southeast Asia fully prepared to trust the White House and the Pentagon and their assertions that intervening in Vietnam was a necessary part of the broadly accepted strategy of containment. At the same time, they went in with the strong conviction that by covering the war independently and honestly (for the most part, there were of course toadies and lickspittles among the journalists too) they were doing what Americans expected, largely because most had little inkling of the level of lying and mendacity that would characterize the handling of the war. And the military had yet to get the idea that it would be politically acceptable to run roughshod over the press, who at that time still had enormous clout given the concentration of media power in so few hands and the public’s general support of the news organizations. People like Chet Huntley, David Brinkley, and Walter Cronkite were not just well-know, but also revered by many, and papers like the New York Times and Washington Post had a lot of cred and influence.
What happened in Vietnam though was that by around 1968-69, probably somewhere after Tet, the journalists in country became convinced that not only was the war not winnable, but that the US military and political machine was actively covering up things and flat-out lying to everyone. They knew this because they were out there with the troops, and they had connections throughout the system. They also still had an audience back home who believed what they read in the papers or saw Cronkite tell them on TV. Even as the country was wracked by social unrest, there was still the broadly shared idea that somewhere out there there was truth, or at least a reasonable facsimile thereof, and that the press had a duty to convey it to the masses.
Of course, we know what happened after all of this. In the aftermath of Vietnam, including stuff like the fallout from the Pentagon Papers, the anger of the media over being hoodwinked by the military, the anger of the military about the way they were (often accurately, sometimes inaccurately) portrayed in the press, and other forces started to erode the status of the press in the broader public.
Once the conservative reaction to the post-Vietnam malaise and the brief liberal interlude of the Carter presidency hit with Reagan’s election in 1980, the Republicans began a war on the press that has continued to this day. It wasn’t hard to get the now all-volunteer military to drastically curtail journalist access on national security grounds, bogus as they usually were. More significantly, in my view the right was able to undermine public faith in the press, aided and abetted to be sure by the venality and avarice of the media moguls who found that the era of 24/7 cable and the rise of things like CNN severely undercut the economic value of expensive high-quality newsrooms. Cable news in turn, with its need to fill every minute of every day with something, anything, further eroded trust in the news, as stuff that never would have made it past the gatekeepers ten years prior was not front and center. Eventually, by the time you get to Desert Storm, the news had become a profit center and the priority was, at the top at least (a lot of journalists were still good, I think) to get access to visuals and stories that would boost ratings. That played into the military’s desire to limit media access, and so the bartering was pretty much a case of access to cool video ops in exchange for effectively censoring or preventing any real combat coverage or deep analysis from the warzone.
The internet of course just exacerbated everything, and the rest is history as they say. But tl;dr, Vietnam took place in my view at a particular juncture of public and private sensibilities and American culture that have never been replicated, and frankly probably never will be again.