I just ran the following command:
pip install -U steem
and the installation worked well until it failed to install pycrypto.
Aft
If you already have Visual Studio Build Tools installed but you're still getting that error, then you may need to "Modify" your installation to include the Visual C++ build tools.
To do that:
Open up the Visual Studio Installer (you can search for it in the Start Menu if needed).
Find Visual Studio Build Tools and click "Modify":
After the C++ tools finish installing, run the pip command again and it should work.