2) The only "safe" browser is a browser running inside a VM, and even then, your definition of "safe" may vary.
3) At least Mozilla isn't actively trying to harm people's privacy and security:
http://www.theguardian.com/technology/2015/jun/23/google-eav...
http://www.forbes.com/sites/gordonkelly/2016/01/06/windows-1...
4) Mozilla will probably start to gain more popularity once they release servo, their new browser engine. https://servo.org/