This means that companies use mostly Java for Selenium test automation.
Java is not only the most popular language for Selenium test automation.
It is also more robust when used in enterprise projects.
It has mature and powerful IDEs (Eclipse and IntelliJ) too.
When selecting the language to learn for Selenium, keep this info in mind.
Don't select the language based only on which is the easiest to learn.
You may end up learning an easier language that is not really needed on your job market.