And in any case, the World Health Organization (WHO) is not the naming authority for novel viruses — this is the job of the International Committee on Taxonomy of Viruses (ICTV) and in this case specifically the Coronaviridae Study Group (CSG, or ICTV-CSG) which concluded that the virus that causes COVID-19 should be named SARS-CoV-2
The WHO on the other hand is the naming authority for novel diseases, and the name 2019-nCoV for the virus causing COVID-19 was only of a provisional nature, signifying a novel coronavirus discovered in 2019. Official classification of viruses is a scientific process, where the degree of relatedness (of novel viruses to those previously identified) is considered. By actually comparing the genome of the novel coronavirus to the genomes of related viruses, looking at certain replicative proteins, it was clear that SARS-CoV (causing SARS) and SARS-CoV-2 (causing COVID-19) are quite close to each other genetically, even though nothing indicates that the latter is a direct descendent of the former. Both are also much more closely related to other coronaviruses, known to infect Asian and African bats respectively. In contrast, none of them are as closely related to MERS-CoV as they are to each other. On the other hand, these three are more closely related to each other, than any of them are to the other coronaviruses known to infect humans. The three previously discussed (causing major epidemics in recent decades) are zoonotic viruses, meaning they are believed to momentarily “spill over” from animals to humans. The other four coronaviruses infecting humans are common respiratory viruses that circulate continually among us, with symptoms ranging from the common cold (which can be caused by more than 200 virus strains) to more high-morbidity outcomes
It's worthy of note that the "SARS" component is simply from the phrase "
Severe acute respiratory syndrome" - a symptomatic descriptive phrase. Many diseases cause that, not just MERS and Covid-19, pneumonias of all varieties can do that too. It's just that it became an acronym for the disease because nobody jumped out and with a loud enough voice and shrieked "it's called Fred from now on!" instead.
Naming of these things can be entirely arbitrary, illogical, and inconsistent if someone can't take hold of it all (like the ICTV) and try to produce some order and didn't insult anyone.
Eg: the Spanish Flu was named "spanish" because Spain didn't have the level of censorship other countries had during WW1, and reported it more freely. "It's the thing that's being reported in Spain!" and no other reason. There's good reason to believe that the true origin was in the US (but its existence largely hidden by censorship), and should more rightly be called the "American Flu". Which will get people's nose out of joint - a rose by any other name is still a rose, so WTF does it matter? Pick something that doesn't blame anyone, much less effort wasted on nothing.
This effect is MUCH worse in computer virus naming. Each discoverer may not be seeing the whole thing, and probably won't know if some other previous discoverer has already found the same thing, let alone named it. The names are all over the map as to how they've been developed too. Mirai is called Mirai because the author called it that. Others are named for just one of the many things it might do. Others are named for amusing bits found inside the virus. And others are simply random words pulled out of the hat to distinguish them from what that specific researcher has found before.
The upshot? Each computer virus can have anywhere from one to over a dozen different names across the industry. Everyone wants to use a standard naming, but frankly the field makes that virtually impossible. Further, nobody would agree which naming scheme should hold sway anyway. If you picked one, someone would ignore it and just continue on their own merry way.