So poor management. A manager's job is to provide their reports the tools they need to do their job, and key to that is not 'obvious cues' but explicitly stated expectations. Basically the manager didn't manage and substituted a PIP for what they should have been doing all along.

I get what you're saying. But as the person directly involved, and as someone who has managed people over the years since, believe me when I say that the fault was my own.

You're really absolving the employee from any possible blame here. Sometimes people ignore blinking warning lights until they get a wake-up call.