Terminal display changed after wipe?
With MacOS Catalina, the default terminal shell switched from bash to zsh. It didn't migrate existing users, but when you reinstalled Catalina it took the opportunity to update your default. The default prompt for bash is '$', for zsh '%'. Use chsh -s /bin/bash to switch back to your old shell as default. Alternatively, change your prompt by setting the variable PS1. Note that if you stick with zsh, there are some changes like different auto-completion methods. Also, if you had any sourcing files for bash (like ~/.bash_profile or ~/.bashrc), you might have to update them to their zsh equivalents.