1. Brexit hasn't happened yet. I.e. UK has not been able to introduce policies that would make it a lot more competitive and friendly for business than the EU/Germany, make it friendlier for international talent, which is one of the opportunities created by Brexit.
2. We do not know what would have happened had Parliament and civil service been more positive and cooperative on Brexit. It could be a self-fulfilling prophecy - remainers in Parliament inadvertently creating greater uncertainty, which in turn drives business away as the leavers are unable to realistically guarantee a more competitive / friendlier for business Britain in the future.