git log/show etc. replaces the terminal screen

oh-my-zsh executes less with -R flag, You may run unset LESS to fallback to default behaviour.

If you want to make this change persistent, put this command to .zshrc.

Can you try with:

git config --global --replace-all core.pager "less -F -X"

From "How do I prevent git diff from using a pager?":

passing the -F option to less causes it to quit if the content is less than one screen, however after doing so the screen is reset and you end up not seeing the content, the -X option does away with that behaviour.