That number is considerably higher than what I have read in the past. I will repost an older answer on this topic. As noted there, numbers are hard to get exact, but 600 is several times more than what I've aware of (although it may be conflating fraggings with successful fraggings). The references source site won't load for me, but does not appear to be an academic text in any case:

"Fragging", or the attempted injuring or killing of one's own officer(s) and NCOs, is definitely one of those things that sticks in people's minds about the Vietnam War. Pinning down an exact number of fragging attempts is nearly impossible. There were likely attempts which failed and no one knew, attempts unreported, and successful ones that were not identified as such. Estimates for incidents seem to vary, but the most cited places it at 800 fragging incidents for the period of 1969-1972, with the height in 1971, where there were 1.8 assaults with explosives on officers per 1,000 servicemen in theater. Some go higher, but certainly less than 100 officer/NCO deaths are attributed to suspected fragging incidents. Whether or not you consider that to be widespread is, I guess, a matter of perspective, but it certainly fits within the popular image of the military in Vietnam and the breakdown of discipline and morale that captures the popular imagination.

As for the why, motivations vary from incident to incident. The minority of cases were 'lone wolves', some single soldier who acted on his own. In a study done shortly after the war on the American combat soldier, these incidents, which were estimated as making up 20 percent of fragging attempts, were described as follows:

Such individuals developed a diffused resentment against the whole military system rather than toward a specific person—though a particular noncom or officer might come to represent symbolically the system. These were cases in which the perpetrator was likely to be personally unbalanced or psychologically disturbed at the time he resorted to violence. In this type of fragging no collusion with others is involved, little if any warning is given, the lethal instrument is usually one's personal weapon, happenstance often determines the ultimate victim, and the culprit makes little effort to hide his identity.

I'll share one interesting incident I found of this nature, the attempted murder of Lt. Col. Donald Bongers by S. Sgt. Alan Cornett, as, while not a prototypical incident, it provides some excellent quotations. Cornett wasn't a draftee, or even a basic grunt. He had served over six years in Vietnam by the time of the 1972 incident, and was a Special Forces medic. He and Bongers had been at loggerheads for some time as Cornett was married to a local woman, which the LTC disapproved of, referring to Cornett's wife as a "prostitute" and preventing her from coming onto their compound.

Nov. 30, 1972, Bongers gave Cornett a dressing down and relieved him from duty for drinking while on radio watch. In his 'hootch', Cornett got roaringly drunk, and decided simply that "I was really tired of the bullshit, and I told them [the investigators] he was an asshole who deserved to die." He described the next step to the investigators thus:

I kept looking at it and wondering if it was worth it . . . I took the tape off from around the grenade, pulled the safety pin, walked over to the commo bunker, stood there for about fifteen minutes deciding if I should kill him or just throw a scare into him. I decided not to kill him, but to scare him. I threw the grenade down the steps of the bunker . . . I stayed there until the smoke cleared.

although interestingly in writing about the incident later, he gave a very different recollection:

In a cold killing rage, I went to my hootch and grabbed a grenade, walked back to the bunker the XO was in, pulled the pin on the grenade, threw it into the bunker, closed the bunker door, and started back to the hootch. As I was walking back, I heard the explosion of the grenade.

Not immediately caught, he essentially turned himself in when another soldier was accused, although in dramatic fashion by grabbing his M16 and stating "if that is what LTC Bongers thinks, then I’ll kill him for sure.” He was found to be in possession of .16 grams of heroin when arrested, although he denied it was his at trial. Interestingly, at trial he brought in numerous character witnesses to describe him as a good soldier, and paint Bongers as a racist asshole who treated Cornett unfairly, and even more amazingly, his sentence was only a year hard labor with no pay, and reduction to lowest enlisted rank. He was given the chance to join the U.S. Army Retraining Brigade at Leavenworth, and was allowed to reenlist, apparently retiring as an E-8 after 20 years service. An incredibly atypical case, in its result, but again, insightful into the mind of the soldier at the time.

The majority of fraggings were coordinated within a small group of soldiers, usually motivated by some perceived transgression against the 'group integrity' represented by the officer, and unlike the happenstance aforementioned, usually conducted with preplanning while in camp. A Leeroy Jenkins type LT, whose men felt was reckless and put their lives at risk, might be targeted, although it was more common to see fraggings perpetuated by support troops than combat infantry. Likewise an officer who was too much of a disciplinarian, such as enforcing military anti-drug regulations, might also incur the wrath of his men. Some cases were driven by racial motivations, usually African-American soldiers seeking retribution against a superior who was considered to be racist. Unlike the 'lone wolf' operator though, the perpetrator was often not clear, and would remain at large, obscuring the precise motivation of a given incident, not that people weren't willing to guess.

In the cases where the perpetrator was captured and their motives discovered, it is notable that there was often a confluence of reasons. While in most cases, the perpetrator had had a negative confrontation with their target within the past few days - whether a feeling of being 'scapegoated' for some offense, or dissatisfaction with their roles in the unit - it was the group environment that could help push them to retaliate after whatever perceived slight had sparked them. And while "insensitivity to the frustrations of the men" was the most common reason given, "boredom, monotony, and inactivity" was often cited as a motivating factor in moving from mere grumbling to action.

Regardless of whether part of a group action, or singular motivation, nearly ninety percent of 'fraggers' caught were found to be on drugs or drunk when doing the crime, and it was often men with slim prospects. In his study of convicted 'fraggers' done just after the war (although he doesn't provide too much detail, it seems that they were disproportionately of the 'lone wolf type', and Dr. Bond himself cautions that the fact these men were caught is itself an important variable), Dr. Thomas C. Bond described the typical example as:

men [who] had experienced rejection and disappointment throughout their lives and demonstrated a low tolerance for frustration when their underlying dependency needs were not met. They were largely loners, having few friends, and often expressed feelings of inadequacy and anxiety in groups. These men viewed enlisting in the Army either as a way of escaping from problems at home that they were unable to resolve or an attempt to prove their masculinity and independence. When the military failed to meet their expectations, they became more despondent, focusing the reasons for this failure on external authority figures.

½

Here is the source (go to the Wayback Machine to retrieve dead links like this). I'll let the reader judge how reliable that source is, but as a Wikipedia editor I would consider it worthless and unusable, as being likely biased and with no way to know how rigorous their fact-checking operation is (but the site doesn't look very professional).

Their figure of over 1000 at the lower left is not supported by the one link they include...

...this one to a mid-1971 article in Armed Forces Journal which says "the Pentagon has now disclosed" these numbers: 96 fraggings in 1969, 109 in 1970, and "authoritatively estimated to be running about one a week" in 1971 which of course we be about 50 for that year.

That's a whole lot less than the first source, and that source is a lot more reliable is my guess. "the Pentagon has now disclosed" is not something that the Armed Forces Journal would lie about, probably, nor would I consider it likely that they would make up, spin and cherrypick, or be sloppy about figures they claim to have come from the Pentagon, as that would not fit their publication model and if done generally would probably lead to bad outcomes for them eventually.

Where the Pentagon got those numbers I don't know. The Pentagon could have some incentive to, let's say, set a overly high standard for what is considered an established incident in order to lower the numbers. Or they could just have honestly flawed methodology.

(However, don't imagine the Pentagon would be likely to keep two sets of books, that sort of thing. These people are orderly and do not like to violate protocols or reporting laws and do not usually piss in their own soup when gathering data for their internal deliberations. Of course these are human beings so anything is possible.)

Whether there were incidents that weren't reported as such or if so how many I don't know. Seems possible. It would be hard to know for sure I would think. I do know that the Army took the general situation very seriously indeed, and this led to some important changes, but I don't have the sources or expertise to expand on that.