Python level is different.

echo %PATH%

You should check the PATH environment variable value with PATH and maybe the pass of Python 2.7 is ahead of the pass of 3.8, so that's how it works.

To use multiple versions of Python on Windows, you can use Python launcher.

py -2.7 python2script.py
py -2.7 -m pip install package2install

py -3 python3script.py
py -3 -m pip install package2install

You can use it with .

If possible, it is a good habit to create a virtual environment and activate it.