Part of the cause is that the people doing this still benefited - if you can cut a bunch of costs and bump profits for the next few years it doesn't matter to you as an executive whether those changes ultimately lead to significantly worse outcomes for the company in the longer term.
Brand loyalty takes a while to fade, there seems to be a cycle with a large number of successful companies that goes
work honestly to build a good product
-> generate brand loyalty
-> people with integrity get replaced by people who would have had no chance of building that successful product/company in the first place
-> cut as many corners as possible while riding the brand loyalty to more short term profits
-> eventually, on the scale of decades sometimes (because people take a /long/ time to realize that 'well known brand' !== quality), get out-competed by a small company building the same thing as you with integrity
-> return to step one with new company.
Brand loyalty takes a while to fade, there seems to be a cycle with a large number of successful companies that goes
work honestly to build a good product
-> generate brand loyalty
-> people with integrity get replaced by people who would have had no chance of building that successful product/company in the first place
-> cut as many corners as possible while riding the brand loyalty to more short term profits
-> eventually, on the scale of decades sometimes (because people take a /long/ time to realize that 'well known brand' !== quality), get out-competed by a small company building the same thing as you with integrity
-> return to step one with new company.