On Apple Silicon machines, Homebrew installs itself in `/opt/homebrew` rather than in `/usr/local/bin` as on Intel-based machines. I suspect that you are running on a Silicon machine. The `/opt/homebrew/` directory isn't part of the standard `PATH`. To accommodate this, it is suggested to setup a `~/.zprofile`:
> Add Homebrew to your PATH in `~/.zprofile`:
>
>
> echo 'eval "$(/opt/homebrew/bin/brew shellenv)"' >> ~/.zprofile
> eval "$(/opt/homebrew/bin/brew shellenv)"
>
(the first line adds the code to `~/.zprofile` and the second runs it in the current shell)