Standards for comma usage weren't established until almost the end of the 19th century. Some people used breathing or personal stylistics to decide on comma use, but there certainly was no general expectation that it would follow grammatical construction or logic.
Compared to some other 18th century documents I've read, the US Constitution is downright spare with commas.
Compared to some other 18th century documents I've read, the US Constitution is downright spare with commas.