[ConservativeMind]

Then why did the states leave it, and one by one, join another union?

They weren't supposed to do that according to the perpetual union.

Correct, they did so without passing through the agreed Constitutional processes.

[jeffersondem]

“Correct, they did so without passing through the agreed Constitutional processes.”

And, they did so without passing through the agreed Articles of Confederation processes.

So the states seceded and nothing bad happened.

The northern states supported secession. And the southern states supported secession. They all agreed to secession and nobody went to war.

And when the new union was created, the states did not repeat the use of the failed word perpetual in the U.S. Constitution.