Picture this; DNC knows it has been hacked and it was an insider (Seth Rich?), how can we blame this on Trump and take the heat off ourselves? Let's set the groundwork for a claim that Trump worked with the Russians to facilitate the hack and undermine the election. The meeting is the important thing, not what happened at the meeting - just the fact that it happened. They set up the meeting (it is already known that the Russian lawyer has connections with Democrats and is anti-Trump based on social media accounts). They push the meme that there was collaboration with the Russians, having the evidence of the meeting in their back pockets to spring at the right moment. The Russian meme starts to die peter off due to lack of ANY evidence, so time to spring the info on the meeting to bring the meme back to life.
The problem is that the email that invited Don Jr. to the meeting explicitly said that the invitation was being sent because of the Russian Government’s support of Trump. That sentence seems like a red flag to me — if they really were cooperating they wouldn’t have said that. But it’s not just a case of Don Jr. looking for dirt on Hillary. The problem is the explicit claim in the invitation that the Russian Government was supporting Trump and the fact that Don Jr. didn’t back away when he saw that.
See 16. There was no hack and an insider breach, as you suggest, is a leak.
Confusion of the two doesn't help.