The Egyptians were warned that the plague of Barad was coming, and those that feared Hashem's power brought their livestock in from the fields. Shemos 9:20-
It's interesting that Iyov makes an appearance in the story of Klal Yisrael's sojourn in Egypt. But this is not the first time he appears.
When Pharaoh first discussed the Jewish problem with his advisers, the Gemara (Sotah 11a) says that these advisors were individuals we are familiar with: they were Bilaam, Iyov, and Yisro.
What, exactly, was Iyov's sin? He stood by and did not stop a רודף. Was this a sin of omission or a sin of commission? Did his silence do nothing, and he was punished for not making an attempt to fight the decision, or did his silence encourage and contribute to the enactment?
In other words, did he have a duty to actively oppose it, and he was punished for failing to do his duty? Or, or was he punished because his silence was interpreted as assent, or at least as indifference, and his indifference/assent factored into the decision to crush the Jews?
The reason I ask is because if Iyov was a yarei shamayim and a decent man, it's hard to believe that he would have allowed his silence to contribute to suffering. (The Ben Yehoyada in Sanhedrin does say that Iyov's silence contributed to the enactment) If, on the other hand, it was just a a matter of not caring, it's still surprising, but I can conceive of the possibility: A Yarei Shamayim would not have participated, but a Yarei Shamayim might have been indifferent. They weren't his people. Every day injustices take place in the world, and we simply don't pay attention. We could go out and protest. We could march in the street and yell about the suffering in Tibet or Africa or India. But we don't. We have our own people to worry about, and we can't fix the whole world. The reality is that in life, there are disasters, and we don't lose a moment of sleep over the suffering of strangers on the other side of the world. So what was the complaint against Iyov? Why should he have endangered himself on behalf of the Jews?
that failure to protest where you can make a difference makes you liable for what follows.
Similarly, we find that Aharon was punished for his silence, in Bamidbar 12:1, where the Shach al Hatorah says
But what is the extent of this obligation? From the fact that Yisro ran away, it appears there was danger in opposing the decision. If there was danger in protesting, what was Iyov's duty? We, that we have a halacha of (Vayikra 19:16) לא תעמד על דם רעך, and most likely (See Choshen Mishpat 426 and thousands of Rishonim and Achronim) we're allowed to endanger ourselves to save others, but we're not obligated to endanger ourselves in order to save another person. So what was wrong with Iyov's silence, if speaking up would have been dangerous? Let's assume, then, that there was no danger to Iyov. Why did Yisro run away? I don't know. Maybe that was after the majority decided. Or it was a middas chasidus. But it's most likely there was no danger to Iyov, and he was punished for failing to protest. To me, it is clear that Iyov suffered for his indifference, for his failure to at least cry out against the injustice, even if he couldn't do anything about it, as the Brisker Rov said.
Here are some suggestions.
1. It could be that for the average man, there is no din of Arvus outside of what the Torah is mechayeiv. But when a person is in a position of power, when he is on a consortium of consultants to the government, then he has obligations greater than the man in the street. You are taking upon yourself responsibilities, and you can't then ignore them. For a man in that position, silence is a breach of duty.
2. The Jews were known as rachmanim, bayshanim, and gomlei chasadim, they were a people with a unique bond to the Ribono shel Olam. Even if indifference to suffering is not a reason for punishment, indifference to the suffering of the Jews is a sign that you don't care about the Ribono shel Olam. If you have any bond to the Ribono shel Olam, you love the Jews. So his indifference was a siman- a symptom of a fundamental flaw in your spiritual relationship with the Ribono shel Olam. As the Sh'lah says, ואמר לא תעמוד שלא יתעכב כיון שהוא רעך בתורה ובמצוות אי נמי לשון שתיקה דמך תחת דמו ונפשך תחת נפשו אם תעמוד על דם רעך. It's possible that before Mattan Torah, every Tzadik was a ריע with everyone who did mitzvos. Since Iyov was a tzadik, he was a ריע with the Bnei Yisrael, and the mitzva did apply to him.
3. The punishment for Iyov's indifference was Hashem's indifference. The Satan wanted to torture Iyov, and Middah keneged middah, Hashem said nothing, He simply did not interfere.
4. That all of our proofs from the mitzvos in the Torah, that it's only based on the din Arvus, הוכח תוכיח השבת אבידה and לא תעמד, and we don't find any such dinim by Bnei Noach, are just wrong. It's not the dinim that mandates this behavior, it is essential humanity. Whatever danger there was to Iyov did not justify his silence. If you see an innocent human being suffering, you should cry out in protest. If you don't, you're no better than Iyov.