Why do people explaining separation of church and state ignore the founder's mainly political aim to keep the Anglican church out of US gov?

A couple reasons. First, general ignorance of that particular aspect of the founders' intent. I'd bet not one in 100 Americans could tell you that the colonies collected taxes to support churches, a real sticking point for people who did not belong to the established church in those colonies. Second, the modern Catholic/Anglican churches, and modern-day monarchies, are pretty non-threatening. That during the 18th century the royal adherents of those religions had a predisposition to absolute rule is again something most modern Americans don't know. Finally, so many of the founders may have been baptised Christians but were in fact philosophical deists (as opposed to atheists) that their works can be cited (usually out of context) to make them seem anti-religious.

Mostly because it's bull. It wasn't that hard to break off the American faction of the Anglican church and rename it. What they were actually worried about was the substantial numbers of dissenters from the Anglican church who might try to break off from the new nation if the Episcopalian church was installed as the state church. They'd come out to the colonies in the first place to avoid being under the thumb of the state church and would go their own way if there was a new and more local one.

I am very aware that the reason they wanted a separation was b/c of the violent disagreements between various Xian denominations, not just the one. there's a 'polite' term called the Reformation...what it really was, was a long period in time when the Catholics and Protestants kept fighting among each other. they were also keenly aware of the Crusades which involved Muslims (after all, these were the educated elites of their time). some were Jews and as a group they were NEVER treated well as a whole in Europe. their personal reasons may have differed somewhat but they generally agreed that religion SHOULD NOT be able to dictate to the government. Even the Xians were against it b/c they saw the government as a force that would corrupt their religion. It wasn't just ONE denomination they were worried about. It was several, and some had other motives completely.

If that was their purpose, why didn't they just say so? Do you think the founders were shy about saying exactly what they meant? They seemed pretty damned bold to me in everything they said. If they weren't afraid to speak their minds about England itself, why would they shy away from saying something that offended England's church?

True. Presbyterian Calvinism was the defacto religion of the country until the courts after WWII stated taking the first amendment seriously.

The Founding Fathers were most deists, a few were openly atheist.

What King Apologist said. They were writing a constitution, not a bible. They intended to make themselves clear.