Bbtengineer, what you say is fair.
But to arrive at the discussion about the "why", first we needed to establish that the controller should have sorted Lufthansa into the arrival sequence. Already this was disputed by many contributers.
Personally I still have the feeling that is was more a problem of unwillingness by the controllers side and not a problem of unableness. But this is for others to decide, if there even is an investigation.
As we have learned the controller anyways has to variably sequence the arrivals, some need more space, some less. Lufthansa would have just been another one with a bit more spacing.