Viruses don‘t necessarily cause cells to die, or go into lysis. Bacteriophages do that, but as the name suggests, they affect bacterial cells, not Eukaryotes.

Ebola is a virus that causes cells to die and burst, which makes it so lethal.

On the whole, though, a virus has no interest in killing its host because the dead can‘t spread the virus. So most viruses that affect humans, including Covid, use different strategies. They infect some cells but not all, and the infected cells stay alive - although their function is now to produce new viral particles while their normal, healthy function is suppressed.

For the individual person, it then depends on how many cells got infected and which type they are. We know that SARS-CoV19 likes to enter the cell through the ACE surface protein. Different people have different amounts of these surface proteins on their cells, and in different tissues. E.g. if you have lots of ACE surface protein in your nose and lungs, then those tissues will be mostly affected. If they are absent there but you have some in your bone tissue, expect that area to be affected by the virus.

Then there are those who have very little ACE surface protein in the first place, so they don‘t experience many symptoms. This doesn‘t stop their immune system from attacking the intruder and making antibodies, however.

In all that is only part of the story, though. The research is still very much ongoing and there is not yet a conclusive answer for why some people die from Covid and others don‘t even notice they have it. A few predisposing factors have been identified, but Covid is not only a new virus, it is also constantly changing so that basically both the ball and the goalposts move all the time.