The controller had no way of knowing the TCAS had generated an RA.
There is still no automatic feature in the ATC system (that I know of) that provides this information to the controller.
Technically, an automatic detection of a TCAS RA is feasible through the transponder signal. A TCAS RA is triggered some 50 seconds before calculated impact. The rotation of the radar antenne induces an inevitable delay for displaying the RA on the radar scope, between 0.1 and 8 seconds. The current rule of informing ATC by the pilot is often not followed, or takes an average delay of 30 seconds.
Financially, there appears no willingness to invest in this life-saving feature to automatically inform ATC of a TCAS RA.
Safety is not always priority number 1 in aviation.