SetViewXml not working

I'm trying to use GetViewXml with SetViewXml. To change a 2 to a 1. So. You can already see the difficulty.

This is what I came up with. Can anyone tell me why it doesn't do anything, like throw an error?

$allView = $list.Views["All Documents"]
$allView.SetViewXml( $allView.GetViewXml().Replace("BaseViewID=""2""", "BaseViewID=""1""") )
$allView.Update()