Help in updating multiple person field via powershell - Only updates one user

Im trying to update multiple person field but it only updates one person not multiple users.ONLY THE LAST ONE

As you can see below i'm picking up display name from a field "Contract Viewer" which has values like so: "abc,def,ghi"

Sure i'm missing something.
Thanks in Advance


See code below:

    function Update([string] $itemid)
       {
       [Microsoft.SharePoint.SPFieldUserValueCollection] $ReviewersList = New-Object Microsoft.SharePoint.SPFieldUserValueCollection
       $CMRSItems = $list.Items | where  {$_['ID'] -eq $itemid}
       $CMRSItems | ForEach-Object {
       #my real values are like this "abc,def,ghi"
       $realval =  $_['Contract Viewer']
       #$split = $realval.Split(";#").Trim()
        $array = @($realval.Split(','))
            for ($i = 0; $i -lt $array.Count - 1; $i++)
            {
                $number = $array[$i]
                $user = getSPuser -webURL $webURL -displayname $number
                #Check if user exists
                if($user -ne $null)
                {
                #Get list from Ensurer
                $userlist = GetReviewLists -user $user
                Write-Host $userlist
                #add userslist
                $ReviewersList.Add($userlist)
                }            
            }
             Write-Host $ReviewersList
             #Not sure its aoonly updating the last one
             $CMRSItems["Contract Viewer1"] = $ReviewersList;            
             $CMRSItems.Update();
             $web.Dispose();
        }       
    }
     function getSPuser([string] $webURL,[string] $displayname)
    {
        $user=Get-SPUser –web $webURL | where{$_.displayname -contains $displayname}
        $email = $user.email
        return $email
    }
    
    function GetAllItems()
       {
        #this loops through items from 1 to 2 for example
        $CMRSItems = $list.Items | where  {($_['ID'] -gt 0) -and ($_['ID'] -le 2)}
        $CMRSItems | ForEach-Object {
        Write-Host "RefID: " $_['RefID']
        Write-Host "ItemID: " $_['ID']
        Update -itemid $_['ID']
        }
    }
    function GetReviewLists([string] $userlist)
        {
        $spUser = $web.EnsureUser($userlist)
        $ReviewerValue = new-object Microsoft.SharePoint.SPFieldUserValue($web, $spUser.ID, $spUser.LoginName)
        return $ReviewerValue              
        }
    GetAllItems

`