It's a weird article because he muses about what the causes might be, and quotes/links Corey Doctorow. If you follow the link Doctorow explains what he thinks the causes of enshittification are. Very broadly they boil down to monopoly/market power and governments either crafting the law to favor big tech or failing to enforce it when it doesn't.
Doctorow is right and it basically all comes down to competition. Internal politics or internal anything aren't really the pivotal factor in product quality. To understand this you have to look at the market not just one company in it. If Company X has a lot of competition and product quality is required to beat them, it'll inevitably improve its quality or die. But put that same company in a situation where they have no effective competitors and it's virtually guaranteed that product quality will start to slip.
Stuff like "oh they have good engineers and give them the time to make stuff better" is an effect not a cause. Competitive marketplace -> investment in R&D -> higher quality products.