The significance lies not in the severity of the violation but in the way it illuminates the bigger picture.
The bigger picture being Donald Trump is not the media's President nor almost half of this country's citizen's (legal and illegal) President?
The bigger picture I had in mind when I said "bigger picture" was the landscape as the investigators view it. I'm not talking about Trump and/or his supporters, or the media or the big public picture. My comment was prompted by something one of the talking heads on one of the cable networks said (I do not remember which one).
The speaker was a former investigator. He talked about the investigative process. He talked about how a detective or investigator will follow leads and rule people and facts in or out as the evidence dictates. Over time a set of facts emerge and the case is developed. Or, insufficient facts emerge and the case is dropped because there is insufficient evidence to support a charge.
The speaker also talked about how a fact uncovered later in the investigation can illuminate facts previously discovered. That is the illumination I spoke of above.
Here's an analogy. Innocent Joe, a mechanic, quit his job at NSB Auto six months ago to work at a different shop. Recently, a burglary happened at NSB and a bunch of tools were stolen. A witness observed a black pickup parked behind NSB the night of the burglary. Workers at NSB told investigators that Innocent Joe had a thing for nice tools. He loved it when the Snap-On truck pulled in. He always asked to see the new tools other mechanics purchased. They noted that only the best tools were stolen that night.
Investigators took that as reason to question Innocent Joe who, as it turned out, does not own and never has owned a black pickup. He told investigators he and his wife were out of town the night of the burglary, visiting his cousin and his wife. In a separate conversation Joe's wife said the same thing. When investigators called, the cousin confirmed Joe's alibi. Yes indeed, the cousin says. Joe and his wife were with us that night. They cooked out in the back yard, marked the birthday of one of the nephews with cake at the meal, watched a game and stayed overnight. Satisfied, the investigators rule Joe out as a suspect.
Two weeks later the witness happens to see that same black pickup at Walmart. He remembers it because of the distinctive custom wheels that caught his eye at both sightings. He gets the license number and notifies investigators. When investigators run the tag, it turns out that Joe's cousin owns the truck.
That fact, discovered later in the investigation, now illuminates the facts previously gained and raises additional possibilities that will now be further investigated.
Before, Joe was innocent and ruled out. Now it may be the case that Joe, his wife and cousin are all in on it and lied to investigators. The new fact raises the possibility that there was not one burglar but two. It may be that this case will grow from a simple burglary to one of burglary, conspiracy, transporting stolen goods across state lines and lying to investigators.
That's what I mean by illumination. A fact discovered later in an investigation casts previous facts in a new light.
The email chain released by Trump Jr. introduces a new set of facts that serve as a new source of light. That light will illuminate previous facts and previous explanations in a new way.
For example. It is a fact that Kushner did not disclose his meeting with the Russian attorney on his security clearance form. His initial explanation was he forgot about that meeting. When others made the meeting publicly known, Kushner modified the form to include the meeting.
Now that Junior's email chain is also a known fact, investigators will be less willing to believe that Kushner simply forgot about the meeting. It is now known this was a gathering of three top campaign officials, planned in advance and confirmed in writing with a stated purpose and guest that a reasonable person would consider memorable if not exceptionally so.
While the results of the meeting were inconsequential (according to Junior), the expectations about the meeting were high enough to plan the meeting in advance and bring three top people off everything else in the white-hot heat of a campaign and into the room to meet the Russian attorney. "I forgot" is not as believable as it was before the email chain became known.
With this and many other aspects of what is being investigated, the email chain casts things in a new light; a light that will likely increase investigator skepticism, open new paths and prompt them to keep digging.