Well pyenv is to manage multiple versions of python, virtualenv is to create virtual environment, venv is virtualenv added to the stdlib, you forgot pip, virtualenvwrapper and mkvirtualenv are management tools for venvs and pipenv is also that but integrating pip.

There's pyenv, pip and virtualenv/venv (same thing) and then there's a bunch of tools to make them more implicit or ergonomic (if you like the way these tools work more than the base).

So really there's not a multitude of competing standards, there's 2/3 complementary standards and then people building their own tools atop that, not entirely unlike the multitudes of Jabber or Twitter clients we used to have.

Things were worse before virtualenv rose to prominence.