Orks don't respect a lot, but what they do respect is strength. Show how strong you are and you'll get a following of Orks in no time. So, it's no surprise that Mozrog Skragbad has a following, since he's shown to be the strongest, toughest ork around. Get a look at his stats in 40k, along with those of his mount, the Great White Squig, in this article.
From the article:
The legend of Da Great White Squig has been told by Beast Snagga Orks for many years and now, as fresh new hordes of monster-hunting Orks flood the Octarius sector, the truth behind the myth emerges once more.
To those Snakebites who fight under him, Mozrog Skragbad is a totemic figure blessed by both Gork and Mork, not to mention the ‘ardest git in the galaxy.* Now almost entirely bionics, scar tissue, and bad attitude, he’s legendarily tough, even by Ork standards, and bullets, lasers, and rockets seem to bounce harmlessly off him.