The framers didn’t anticipate armies becoming permanent institutions, which is why we have a “no standing army” requirement that we just kind of ignore. But even that only makes the second amendment clearer: if you don’t have a standing army, who has the guns? The answer is militias comprised of heavily armed citizenry.

You seem to be ignoring the concept of an armory (the local Armory food hall used to hold weapons) which does not require individual ownership of the heavy arms, not a standing army.

Also there is no "no sanding Army" requirement. There is only a requirement that the army can only be funded for 2 years ahead, presumably to require ongoing consent from Legislature, to prevent a Chancellor Hitler-type situation or a President becoming King by getting a huge multi year funding and then turning against the future Legislature and the country.

I am pretty certain that the large military powers at the time (England, France certainly Prussia) had standing armies already. So I would be highly surprised that the founders did not anticipate armies as a permanent institution. That would be a pretty big blind spot, considering they already existed.

They Constitution (and the framers) opposed the President having a standing army. It supported the country having one with biannual renewal of consent from Legislature for funding.

And the War of 1812 taught President Madison the danger of being under militarized and over-reliant on militias.

In some ways, the Founders were delightfully naive. Kings also already existed, and they'd just thrown off control of one.

Many Founders believed a standing army to be an inherently corrupting force (if you have a warrior class, sooner or later they will make you go to war) and thought America would be better without one. Whether or not that could have been true in the abstract became irrelevant because the need to perpetually defend territory meant that there was never an opportunity to disband the Continental Army.

It's easy to forget that the United States of the ratification of the Constitution is a different United States than the one we live in now. Both the Civil War and the radical reinterpretations of several federal powers during the Great Depression fundamentally changed the nature of federal and state government.

The Second Amemdent's in there because without it, the states wouldn't have been willing to ratify a Constitution that allowed the federal government to take their guns away. After all, they had just won a war against a monarch an ocean away; they weren't about to give their power of defense to an executive half a continent away. Remember, there was no guarantee a Constitution was going to happen at all; quite a few compromises and curveballs in that document are there because every single state had the option of rejecting the whole thing and being their own country. Many Founding Fathers envisioned defense of the US would look like individual states generally handling their own affairs, and a national army only being mobilized in the event of a national threat (however, practically speaking, that didn't come to pass... No sooner was the Constitution ratified than Washington led the Continental Army to force the citizens of western Pennsylvania to pay federal taxes).

Gun regulation was properly recognized as a state authority for most of the country's history prior to the Civil War and varied wildly from state to state, with many being significantly more restrictive than modern law. It's only with the passage of the Fourteenth Amendment (and the Due Process clause, "No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law") that the Second Amendment ties the hands of state governments in the same way it tied the hands of the federal government. This restriction has been re-interpreted over the decades, but broadly speaking that's how we got from a 1700s Philadelphia that banned gun ownership for some immigrants to the modern interpretation where even tracking who owns a firearm might be considered an abridgment of the right of ownership.

I think that’s actually a coherent view of the 2A. But when you pull on the 14A incorporation thread quite a lot unravels with it. The Establishment Clause, for example, was intended to prevent the federal government from interfering with state established churches, some of which still existed at the time. It actually makes no sense to incorporate that provision against the states.

Makes no sense other than we had just fought a war over the concept of states' rights overriding federal protections. Hypothetically, they could have narrowly-tailored the 13th through 15th amendments to end slavery and do little else, I think it is possible that lawmakers of the day came to a rational conclusion that the next time the states challenged federal authority so brazenly, it wouldn't be over slavery but over some other issue of fundamental rights... And if the protections laid out in the Constitution were good enough for people when exposed to law at the federal level, they should be good enough for citizens of the states as well. One certainly can't expect that anyone would have benefited if, hypothetically, Georgia were to dedicate itself to Roman Catholicism and declare all federal laws null and void, replaced by the law from the Vatican (a scenario that could have been possible prior to the 14th).

One advantage the chosen approach has is, in a sense, interpretive simplicity, even though in practice it strips much authority from the states and moves it up to the federal level.