Plot twist: the parachute runs MCAS.

Golden parachutes are primarily handed out to those who are hired from the open C-level circuit into a house already on fire. They have the bargaining position to demand the "heads I win tails you lose" contracts that are known as golden parachutes. Someone who internally rose through the ranks never enjoyed that much bargaining power. He surely won't fall into poverty, but landing might not be quite as soft soft as you imagine. (not ruling out the possibility though)

Certainly having started from scratch at the company would help him as a leader as the rank and file knew that he had been in their shoes, at one time. But, yeah, being steeped in the culture may very well have been part of this problem as well.

Boeing and Lockheed aren't merged as companies, they're only combined for building launch vehicles. They created ULA as a joint venture. It was a weird situation where it made sense for both companies— Lockheed basically lost all of their trade secrets to Boeing after they did a crazy amount of industrial espionage. After a few Boeing employees went to jail, Boeing lost all of their launch contracts and were banned from bidding on any for a few years. Even after the ban ended they were in rough shape financially.

Do you mean McDonnell Douglas?

Muilenberg became CEO 18 years after the merger. I wouldn't expect him to exemplify Boeing's old culture. It was also only 6 months before the first 737 MAX flight.