uninstalling bs2 doesn't deactivate it, you have to manually deactivate. For the upgrade version of bs2 you need to keep bs1 installed so that the drm can see that you have a valid copy of bs1.
DCS Product Installation
1- Uninstall all previous DCS products prior to versions 1.2.0 (except bs1 if you have the bs2 upgrade key)
2- To be safe, delete \Saved Games\DCS files
3- Install DCS World 1.2.0
4- Install each new DCS module (1.2.0 or latest Beta version)
cheers :)