How does sudo -E work here?

I executed the following command to add a ppa repository in Ubuntu:

sudo add-apt-repository ppa:ppaname/ppa

This command returned an error that the ppa name format is not correct. Then I looked here and thus, ran the follwing command:

sudo -E add-apt-repository ppa:ppaname/ppa

The above command worked like magic. Then I read the man page for sudo which said that sudo -E preserves environment variables. What I do not understand is how preserving the environment variables helped me here?