If this is something that applies to other German universities, then it could be that Germany has a policy of growing its own researchers rather than importing talent from around the world. It seems to have worked very well for football so perhaps the obsession of British universities with importing international researchers is not such a good idea..
I just wanted to share with you, that we did not acquire two researchers to get on the HCR List to get a higher rank in the Shanghai Ranking. Those two researchers are Prof. Büchel and Prof. Ravens-Sieberer. Prof. Büchel is working at our university for over a decade now and Prof. Ravens-Sieberer is at our university since 2008.
Please also aknowledge, that our place in the Shanghai Ranking was very stable from 2010-2015. We were very unpleasent, when they decided to only use the one-year list of HCR, because in 2015 none of our researchers made it on the 2015-list, which caused the descend from 2015 to 2016.