If people preferred a good paid solution over a shitty free one then Kagi would be a trillion dollar company and nobody would ever have heard of Google. But that's not what people want. They want shitty but free. This is the market working as it should. Enshitification is not something done to us. It's something we do to ourselves.
I hate to break this to you, but in the USA, this has happened multiple times: for instance, allowing Govt to shutdown due to spending limits, to push some extra pain + score political points, and then paint oneself as a savior when the shutdown is eventually lifted.
You could argue that they're not making things worse for the folks that actually matter (and you'd be right), but there is immense hardship and pain inflicted on ordinary people routinely (esp. of late), so I didn't want to leave your comment unchallenged.
Or to put it another way, for a government, cruelty is done for its own sake. In a corporation, cruelty is economically incentivized.
I can also see a "unifying mental model" -- whatever increases the "health" is pursued.
A corporation needs to "feed" on money, so its actions reflect this (e.g. PMs worsening services intentionally, in order to be able to charge more and thereby boost revenue).
A party in power needs to "feed" on support from its "base", so its actions reflect this (you said it best: "for the sake of cruelty")