Where to begin...
First, a pet peeve of mine. WHY ARE YOU CALLING .ToString() ON A STRING???????? It's already a string.
You don't really need ConnectionOptions for such a simple query on a local machine.
...and you mispelled "UserName" in the last Console.WriteLine statement.
A slightly rewritten version of your code:
string userNameEnv = System.Environment.UserName;
Console.WriteLine(userNameEnv);
ManagementScope scope = new ManagementScope(@"\\.\root\CIMV2");
scope.Connect();
ObjectQuery query = new ObjectQuery("SELECT * FROM Win32_ComputerSystem");
ManagementObjectSearcher searcher = new ManagementObjectSearcher(scope, query);
ManagementObjectCollection results = searcher.Get();
foreach (var item in results)
{
Console.WriteLine($"Computer Name: {item["Name"]}\r\nLogged In User: {item["UserName"]}");
}