It is a result of Brexit, as leading part (or all) of a Horizon project is a significant goal of many scientists' careers, and usually brings in much more fundi

It is a result of Brexit, as leading part (or all) of a Horizon project is a significant goal of many scientists' careers, and usually brings in much more funding than doing the smaller parts. Britain lost that opportunity for several years, which will have caused people and groups to move to the EU.