I am not sure that I fully understand Diomond's analysis in Guns, Germs and Steel.
Post 2 isn't really getting at the question. The question is not why Eurasia dominated (which was pure chance) but why Europe was more dominant than East Asia given that they are both part of the same land mass.
Diamond says this was because there was greater competition in Europe. It was divided into lots of little countries so that (for example) Columbus could be rejected by Genoa, go to Spain, and get his expedition funded there. By contrast, China dominated East Asia. When China rejected something (exploration, gunpowder, etc) there was no other country to pick it up. China did not, therefore, have to progress through competition. European countries did and that is why their technology advanced more quickly.
Diamond says that this (rather than things like religion or culture) was what made Europe be able to dominate East Asia during this time period.
This is obviously a very complex argument, but I would recommend that you try and persevere with Diamond's analysis, as he does have the ability to explain complex theories very simply. So much of Eurasian's power relies on complete chance. It was complete chance that Eurasia had more domesticated animals and crops that could be used to sustain human life. This in turn led to their world dominance vis-a-vis other nations that did not have these benefits.