That's because Ozzy was the star and everyone else in his band was replaceable. Even the "tribute" song a couple of posts above yours featured Zack Wylde on guitar. Ozzy just soldiered on.
Aside from the obvious...Randy got killed at the worst possible time...he was on the verge of superstardom. I will say..Sharon Osbourne proceeded to make a “star” out of Osbourne, and she did. After those first 2 outstanding records he did with Randy, they the told the huge lie about how Ozzy “co-wrote those records which is laughable. He couldnt write a song if his life depended on it. Whats even funnier...in late 1979, when they kept calling Rhoads to audition for Osbourne, Randy didnt even know who the hell Osbourne was. He politely said “no thanks”...it was his mother who convinced him to go and at least meet with him....half way thru Ozzys first headlining tour, Rhoads had had enough of the silly antics and Sharons publicity stunts...Rhoads informed them he was leaving the band and going back to UCLA to get his degree is classical guitar. He was getting all kinds of great session offers from other artists when he had his accident...he was def moving on from the Osbourne freak show...