* In 2021, 100% of the world’s top 500 supercomputers run on Linux.
* Out of the top 25 websites in the world, only 2 aren’t using Linux.
* 96.3% of the world’s top 1 million servers run on Linux.
* 90% of all cloud infrastructure operates on Linux and practically all the best cloud hosts use it.
Although you are correct its windows desktop competitor has a low market share, there has been some shift towards Linux derivates such as Chromebooks that captured 10% market share in Q4 2020 and 5.3% in 2020 overall [2]
Firefox is irrelevant. Which explains why they support things like this.
If you can't win by building better software you can win by bullying anyone else who does.