Fan/Media culture has led to ranggggz culture which means players have to win rings or they get clowned for the rest of their life. And now that we have social media, that means you are getting clowned 24/7 until the day you die.
If you want to promote a culture where players stay then you have to praise regular season success more.
Don't the Jazz have the best record over the last 5 years? If that was praised and respected then you might have a situation where Donovan is more likely to stay.
Also Donovan needs a bigger market to achieve individual marketability. He's got a good personality to be marketed, but he isn't a big personality that is going to demand attention in the ways Anthony Edwards and Ja Morant do (absolute insanity Donovan has a shoe deal over those two but that is the importance of timing/luck in life).