I just had the game were I did the test correct and only Silicoids expanded like crazy because they are Silicoids. Normal behavior, the universe was divided in 2, Mrrshan and Darloks voting for Silicoids and Alkari and Bulrathi voting for myself. I won after taking out 4 planets of the Silicoids.

This is more normal for me, I was able to use diplomacy and have half of the universe help me, in thew other game the Klackons had everyone on their side and making them attack me as soon as the test was failed. Also there was no way to stop the war in that first game. On this second one were I had Bulrathis and thew Alkari on my side I was able to stop the Darloks and Mrrshan with a peace treaty but I didnt because they were weak. Mrrshan accepted once and offered a second time.

The thing here is if I do the test correct the AI actually makes war between them and if I fail it literally all the AI are allies and in war with only me.

Second test: I just found what the real problem seems to be. I am doing my second try in average and the problem is not how the AI expands or declare war on you out of nowhere, the problem is how by failing one test actually makes the game go to final war where all the AI's are allies in war against you without saying is on the final war. By doing the test right the AI actually declares war against each other. Try both failing and making the test correct and tell me if you have the same outcome.