The chorus of people asking for increased typesafety had become too loud to ignore. Type hints gave them enough support to cover 95% of their needs, which were/are largely organizational rather than technical: developers must feel sure they are using the right classes in their code, pulled from the right places in their project, and don’t have to look up docs at every step (because the IDE will autocomplete stuff). What happens later, the low-level implementation, it doesn’t really matter; what matters is the information about types is surfaced somewhere, so that IDEs and tooling can use it to document projects and help developers.

That’s what type hints do, and yeah, they are basically glorified docs, but integrating docs into syntax is one of Python’s many traditional strengths (see docstrings, doctests, etc). That’s also why they are optional, thank goodness, so people who don’t have big-org / big-project needs can still be productive.