Juries are completely inappropriate tools for the job of deciding civil trials. Like lots of things that are crazy in the US the Americans did it as a perverse imitation of how England did it back when they became independent.

Today nobody else does this, England for example only really uses jury trial to decide serious criminal cases (for minor stuff there isn't a professional judge at all, a panel of lay magistrates decides, they mostly seem disappointed rather than angry - like parents whose teenager was caught smoking).

I always assumed it's peers as opposed to superiors. I.e. Your jury is not the king and queen but other commoners like you.

Juries are supposed to apply “common sense” as well as evaluate the veracity of testimony. If expert domain knowledge is necessary, expert witnesses will be called to present it. Experts on a jury are a problem because they will essentially provide alternate evidence outside the public court procedure (jury proceedings are secret), and because their expertise is not subject to challenge by the other side. (Imagine the Dunning-Kruger effect in a jury setting.)