Most of those are because the defendant is in a position of weakness and the courts are busy, not because the defendant is able to cut a deal that lets them live out the rest of their lives outside of prison and with billions in the bank.

a plea bargain is by rule a conviction. It is simply an alternative route to one.

A plea bargain is where a bargain is struck between some prosecuting authority and the accused wherein the accused pleads guilty in exchange for some nominally lesser punishment.

WHat happened here is one plea bargain that included (but should not have included by any rational definition of justice) a global bar on the accused being prosecuted for any other crimes. See if you can find an example of that logic being applied to a low level drug dealer or non-rich person.