"because he won the most conference and national championships?"
In 2011 and 2017 he won the national championship without winning the conference championship so it will not be because of conference championships since they do not matter. Conference titles do not matter for national titles, but the win/loss record does. As far as the sport goes, you may care about conference titles more, but the pollsters and playoff committee that rank the teams and determine the national champion do not and never have. You are in better position at 11-1 without a conference title to make the playoff than 10-3 with a conference title. 2004 and 2008 Texas, for example, would have made the playoff, where as 1996 Texas would not have made the playoff.
I will also add I preferred ending the season with a bowl win (which mattered more to final rankings) under Brown than a Big XII title and embarrassing bowl loss that stoops consistently had (which hurt their final ranking).
That's what I want and have always wanted for Texas every single season in every sport. I've never peed myself because we had a 10-win season and a Holiday Bowl victory. (Okay, I never peed myself over anything.) Championships matter to me – and for that I don't apologize.
I want to win the lottery too. However, Nick Saban is the exception not the rule. I hope one day Texas gets a coach that goes on a crazy run like that. However, the likelihood of ANY program getting that is low. Regardless of you program, the next coach you hire will likely average 8 or fewer wins a year and never win a national title. If you get a coach that wins 10 or more games a year, puts you in a position to a national title consistently and actually wins one, you should never ever fire him unless things truly go off the rails (which they did not do here). Otherwise most of the time you are getting 5-8 win seasons and that's what we have gotten most of the time without Mack Brown. Hopefully the next Mack Brown comes along sooner than later and Makes UT Football Great Again.
Long story short, without Mack Brown we do not win any national titles and we lose more of the time so if you expect Nick Saban results, which are not going to happen, I do not know how you are still watching Texas Football in the post-Mack Brown era.
Also, yes, you can fire Tom Landry for Jimmy Johnson if you have a sure thing Jimmy Johnson coming along... but that did not happen with Charlie Strong.