Why do iranians speak french?

Answer 1

They don't. They speak their own languages, for example the Farsi.

However:

The different languages in the world are buildt up like a tree.

We start with the stem, and have different branches of languages from the stem.

Each different branch may have sub-branches.

There are many languages in the world, and some are more similar to each other than others.

People speaking Farsi might find the French language easier to learn than the English language due to similarities in language like words, grammar or perhaps both.

Answer 2

Iranians may speak French for a variety of reasons, such as to pursue education in French-speaking countries, conduct business with French-speaking partners, or for cultural and social reasons. Learning French can also provide access to a wider range of opportunities in diplomacy, academia, and international relations.