When a Bachelor's degree became a proxy for "can show up and complete assigned work" for employers that was the start of its decline as an academic credential.

First it went from "comes from money and has no need to work, whatsoever" thorough "eventually needs to get a job but can live off rich parents for four plus years" before the current state.

Economists call it costly signaling. The more elite of a status it signals, the costlier it can be, but with guaranteed student loans, the economics of it have become so separated that as the eliteness of a bachelor's degree has gone down, the costliness has gone up.

Right. It's like "this person likely has a student loan they need to repay so they will probably come to work."