EXE RUN ERROR
1.) All Nix Repls need that replit.nix file to run anything. In your case, you've just uninstalled Mono by removing that file.
2.) A Bash command is the thing you put in the terminal to do things.
ls is a command.
echo Hi is a command with a parameter. To run Mono projects, you run the
mono command with an exe file as a parameter. You put a Bash command in the .replit file to run things.
So right now you're Repl won't do anything since you not only have nothing installed but you also have a malformed run command. Remake your Mono Repl but don't remove anything from there. Then you'll make the run command run the exe you're trying to execute.