The difficult part of running a ca is convincing others you’re trustworthy. You need to have your business processes audited but an independent third party and then wait for your root to be adopted and deployed in browsers.

The value in exiting providers is their reach; versign for example is deployed in practically every trusted root bundle. When GoDaddy wanted to enter the market, they bought Starfield who already had a root which was widely trusted and crossed that with their own.

The reason people will pay for you to compute a number based on a number they give you and your super secret number is that people trust what you’re doing with your super secret number. And that trust takes time.

And when you want to run a public one, you should learn at least everything that cacert did. They tried hard and still never got included. https://www.cacert.org/ That effort seems to be dying and it's been years since anyone asked me to authenticate them.

Some history here. http://wiki.cacert.org/InclusionStatus And that's before root stores had to deal with Honest Achmed's Used Cars and Certificates.

How did LetsEncrypt get acceptance everywhere?