Your description of Douglas/Boeing history is not accurate.
Douglas had its HQ in Long Beach, CA. McDonnell (in St Louis) acquired Douglas. Then in 1997, Boeing and McDonnell-Douglas merged. Initially, HQ was in Seattle, but after Phil Condit left the CEO position, Harry Stonecipher (previously of McD-D). he engineered the move of HQ to Chicago.
IMO, Boeing's decline started when Bob Woodard was VP and President of the Commercial Airplanes Group. He decided to compete with Airbus for market share, using price as incentive. It resulted in a HUGE financial loss for Boeing in 1997 that took years to recover. It also resulted in the big layoffs of 1998, of which I was one victim.
Since the move to Chicago, I believe HQ has become detached from company operations, and beancounters have taken over from the old engineers that previously rose through the ranks. The resulting focus on quarterly profits likely fed some of the corner-cutting...