Part of it is the standard crisis of capitalism, the profit you get from doing the same thing always declines, so over time you have to push up revenue (increasing prices, forcing people to pay, showing more ads, gathering more data, etc) & push down costs (fire engineers, run on less hardware, etc)
Part of it is capitalisms natural tendency to create monopolies, and the lack of competition in a given field causing the company to then lose sight of what it’s good at to compete in a bigger field.
Part is that interest rates mean loans are no longer cheap, so taking on debt to get customer, to at some point down the line make money, is a less viable plan. Twitter is a special case where the bad loans are because that was the original deal not interested rate related, and Musk is trying to pull all of the enshitification levers at the same time.
Part is that CEOs generally don’t have a fucking clue about their products or what they are doing (it’s a circuit job about who you know/blow, not what you know), so once one CEO starts firing/enshitifying, the rest just copy them so as to not be left out.