With Estonia being a reasonably small country, it only has a population of 1.3 million people. Its native language is limited to around a million or so speakers.
It is notoriously difficult to learn for English speakers. It has 14 noun cases, 25 diphthongs, and three lengths of vowels and consonants. It also has eight dialects and 117 sub-dialects! It is no surprise that a study by the Foreign Service Institute ranked Estonian as being the fifth most difficult language to learn.
The Estonian language is actually very similar to Finnish and also heavily influenced by German. In fact, a third of the Estonian vocabulary is borrowed from Germanic languages.