Tosafos quotes from the yerushalmi that even though a person is chayev for damages that he does while sleeping, that is only if he goes to sleep near keilim so he was somewhat negligent by going to sleep there. But if someone only brought the keilim after he fell asleep and he damaged them, he is patur. The Maharatz Chiyus points out a machlokes between Tosafos and Nemukei Yosef, exactly why is he patur? Tosafos writes "they caused it". Meaning, we don't hold the sleeping damager responsible since someone else caused the damage by putting the keilim there. The primary liability and responsibility for the damage is the person who put it there (but he is probably exempt because of grama), which removes responsibility from the sleeping mazik. Based on Tosafos the rationale to be patur is not "o'nes", rather it is that we don't consider the person who damaged to be the cause of the damage. However, the Nimukei Yosef says that he is patur becaue he is o'nes. Based on this, the maharatz chiyus asks, why does the rambam write that if one's life is threatened unless he takes money from his friend, he is responsible for taking the money. Why don't we exempt based on the claim of o'nes? The Shach makes a distinction between a case where one damages unintentionally to one who damages due to o'nes of his life being threatened. Whenever the action is done with intent, even though he was under duress, he is liable. But when he is sleeping, the action is not done with any intent so he is patur.
This sevara is similar to the concept of mis'asek. When one does a mitzvah and has no intent for the action that he is doing, it doesn't count. For example, if he would be trying to clean out a shofar by blowing through it and it made a sound, even if mitzvos don't need kavana, he isn't yotzei. But if he had intent for the action that he is doing, just that he is forced to do it, the gemara in rosh hashana 28a (kaf'uhu parsi'yim) is clear that according to the opinion that mitzvos don't need kavana he would be yotzei.