It’s not singular, “users” is plural. “A group of users” is singular, but “users” is referring to multiple individuals. The correct verb to use with users is are.
For example, you would be incorrect to say “There is users online”, but you could say “There is a group of users online”.
Context.
Here it’s being used a singular group of things.
Like, a herd of cows is a singular thing made up of lots of individual things.
If you lost 50% of the herd, you wouldn’t say you had fewer herd
You’d say you have less of a herd.
But language is what we make it, it’s why the rules are blurry
It’s not singular, “users” is plural. “A group of users” is singular, but “users” is referring to multiple individuals. The correct verb to use with users is are.
For example, you would be incorrect to say “There is users online”, but you could say “There is a group of users online”.