Lots of theories,
the constitution wasnt ratified till 12 years after independence. The bill of rights wasnt ratified till 3 years after that.
my take is that after the war, the colonies/states put steep property taxes on returned soldiers to try and pay huge federal debts.
There were debtors prisons.
There was a lot of unrest (see Shay's rebellion).
There was no standing army.
The articles of confederation didnt account for internal rebellion so the constitution, and particularly the second amendment was written in part to enable the government to defend it's self (see the Whiskey Rebellion). The constitution also created the first (or second if you count the continental army) standing army.
In 1794, three years after the second amendment was ratified, Washington led a force of 13,000 militiamen provided by four of the new states to quell a rebellion in western PA. The rebels fled before any confrontation happened. There was no repeat of Shays rebellion -
- A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.
Basically, the second amendment was a tool of the government used to quell domestic rebellion.
The English wouldnt come back till 1812.
