It is important to keep same defaults as MySQL. At least for now. As stated right at the top of the introduction in About MariaDB, MariaDB is an enhanced, drop-in replacement for MySQL. This means that MariaDB is designed such that you can simply replace an installation of MySQL with an installation of MariaDB without having to change anything in your application setup or config files. MariaDB offers all of the features available inside MySQL and behaves exactly the same. Plus it offers a completely free implementation of some features only available in the commercial (paid) version of MySQL Enterprise.

The issue of conflicts (like using the same port) does not arise, since for most installations only one or the other will be installed: MySQL or MariaDB. That said, for testing, comparison, and development purposes there may be a need to run both, or even multiple versions of MariaDB on the same server and it is possible to install both MariaDB and MySQL, or two versions of MariaDB, in such a way that they both coexist side by side but it is not recommended for the majority of users.