No doubt victim to the success of LetsEncrypt and good riddance, too. Before LE, Starcom was the only way to get a free and recognized SSL certificate, only it was a pain to use (client certificates) and only worked with specific browsers.
I think this had less to do with Let's Encrypt, and more to do with the fact that StartCom's root certificates were distrusted by nearly all major browser vendors some time ago due to [their parent company's violations of the Baseline Requirements](https://wiki.mozilla.org/CA:WoSign_Issues).
They were shady bunch long before WoSign acquired them. I say good riddance to them and their practices.
It was much easier to use than LE for me. I've never had a problem with client certificates. It's awesome technology and it's a pity that it's basically unchanged for years, while insignificant things developed. It could completely replace login mechanism everywhere with much more reliable and secure way to handle credentials.
Victim of their own violations of the BRs, leading ultimately to the "distrusting" of their roots by the major browsers.
Unfortunately usability was the least of its problems.