Why is someName variable not available as soon as I set it, but it is in another job?

source:

steps:
- powershell: |
    $rsdate = get-date -format "yyyy-MM-dd HH:mm:ss"
    $testVar = "hello world - $rsdate"
    Write-Host "##vso[task.setvariable variable=someName]$testVar"
    "some name: $(someName)"
    

- powershell: |
    try {
        "some name: $(someName)"
        "rs date will be blank here: $rsdate"

        if ("$(someName)" -like "*hello world*")
        {
            "dates equals - $(someName)"
        }  
        else
        {  
            write-error "test error"
        }

        dotnet --list-sdks
    }
    catch {
        throw
    }