Besides that picture about Chad's orientation, there were many pictures of Arieth's infidelity that should have sparked a new war between DIKs and Jocks. The same episode shows that the fraternities are constantly feuding over girls and these pictures were supposed to provoke a war again.
But probably Chad decided to attack MC first and disrupted the plans. He was suspended and the war didn't happen because of that. And the attackers had to adjust their plans. And already in the 4th episode there was a direct hit on DIKs themselves.
There were 2 "letters" - one for Chad, contents of which he never revealed and we never learned (for obvious reasons) and probably he hidden that he got something. But the letter for Dawe contained photos with his girlfriend - Arieth, being with 3 (or 4, if Derek had sex together with Jacob with her depending on MC choices at the DIKs party) and Chad gave this letter to Dawe. This one was intended to provoke the fight between the frats. Because this started more that year ago after Tommy fucked the Arieth.
And what do we have in the end?
The jocks lost their influence.
DIKs lost influence.
And who gained influence? The dorm girls. It was their party in ep8 that drew a lot of people because DIKs didn't have parties. And no one goes to jock parties except the jocks.
In favor of this theory is the fact that posters with DIKs appeared after the Halloween party when it became clear that DIKs returns and becomes the center of attention again.
...

What influence AAAs lost? Their president was replaced, nothing happened at all.
DIKs lost the place for parties and yes, they was off the game for a couple of months. Yes, somebody obviously hate them for their best parties and want them to go down.
All the bullshit theories about BBBs, Vinny, being the ones, who trashed their mansion, etc were gone to the trash after EP10.
So the AAAs was the ones who made a revenge on DIKs and put them off the game for months. But the AAAs were provoked to do that in some way. But if DIKs wouldn't trash AAAs mansion with dildos then DIKs mansion wouldn't get trashed too. So, don't far fetching this. Partially it was a Quinn fault, as well.
There's a lot of reasons why the dorm girls decided to do this.
1) Revenge. Rusty and Tommy get laid a lot, a large number of girls came out of the mansion to a DIKs song. Probably some of the girls were really into Tommy or Rusty. Some of them just hate DIKs. For example, we know Becky is friends with feminists. And as we see DIKs and Jocks often feud and bully them.

Dorm guys are fucking around not less than DIKs, I bet even more. Becky what? emm... Becky have nothing with feminists. She is stupid bitch running around for "popular" guys. Silly, pathetic, stupid cunt.
2) Their own sorority. The girls in the dorm probably want to start their own sorority. But maybe the college either doesn't have room or there's a limit on student organizations or some other reason and in order to create one they need to destroy or at least weaken one of the fraternities. In fact, I think there's going to be a strike against HOTs soon.
Then they have to target the HOTs... why DIKs? How DIKs prevents founding and starting the SORORITY? No one would mind, I suppose. But Becky, for example, believes that sisterhood is a relic of the times.
You need to make up your mind who is want what and why, particularly.
In short, the tracks lead back to AAAs. They have the motivation to hate DIKs and shit on them in every possible way one way or another. They agreed to Sage and Quinn's terms, but continued to shit behind their backs. Well, except that they refused direct physical actions by putting a jacket on Caleb.
So, AAAs knowing and able to use some person (girl) that could act as a rat is the most plausible explanation at the moment.
Beth... well, she is a good candidate to be used this way. She is far from pretty and not so desirable one. She is not ugly, but below the middle league.