

Because web browsers are stupidly complicated and expensive to maintain. The only real competitor is google who has infinite money to maintain the chrome superiority and you need resources to maintain safety, fix bugs, and adhere to new standards, which get every time more complex (also thanks to google that doesn’t want competitor). You need a lot of budget for that.
What you say is right if you care about discussing political opinions online. If you only care about memes and general discussions, you don’t create echo chambers