Compared to the brutal murder of an American with cutting his head off, the tortures of Iraqis in prisons started looking like minor pranks of undisciplined soldiers. Another factor was that the beheaded victim was a Jew, which was picked up by the Zionists immediately to justify their actions and to show what kind of enemy they have to be dealing with.
http://www.globalresearch.ca/articles/SAT405A.html

However, so many questions arose about the videotape that all accusers of so-called 'Islamists' got quiet right away and the subject disappeared from the agenda in the world’s media.

The weapons that the murderers were holding in their hands resemble AKs, but the experts claim that this is a modified AK-47, Israeli-made Halil.

All Islamic organizations, including the ones accused of terrorism, have condemned this act. Nothing has been heard about Abu Musab Al-Zarqawi for the past few months, and there has been a rumor going on that he died in a bombing.

But if he has nothing to do with it, and somebody decided to use his name, then it would be quite natural to expect Zarqawi to deny the allegations about his involvement in Mr. Berg’s execution. But no denials have been heard. Especially when such a denial would have been appropriate after all Islamic organizations and the Iraqis condemned this murder.

This fact means that Zarqawi may not be alive. Those who put on that show knew that Zarqawi could no longer deny whatever they accuse him of.