So it looks like that the assassin almost certainly is an individual who is personally affected by the business practices of UnitedHealth, directly or indirectly, and/or got radicalized online and developed a fixation on the CEO.
In any case, it moves the motivation for the killing from a purely criminal to a more political/terrorist motivation.
A strictly personal grievance arising from personal relations seems unlikely given the circumstances.
Here is more from someone who seems to know what he's talking about:
CEO shooter labeled a 'doofus' by expert arguing against professional killing theory
Tom Boggioni
December 5
"The exercise to clear rounds are tap, rack, bang and that's drilled into you when you're an agent or officer," he elaborated. "Tap, rack, bang –– he doesn't do that. He racks the gun, the slide, and then he slaps the top of the gun, the top of the slide a couple of times. There's no trained shooter that would do that."https://www.rawstory.com/brian-thompson-ceo/Edit: Just want to clarify that I'm referring strictly to the way the author describes how the gunman cleared the jam and I take what he writes at face value.
He is completely wrong about the gunman not taking a shooter's stance - having lived in Manhattan for years, I can guarantee that taking up a shooter's stance is a great way to focus all attention on oneself on a Manhattan street, nonchalance is key and a suppressor helps.