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.