BtS requires some files from Warlords - when you install BtS without Warlords present it simply installs a mock Warlords install with just the files it needs. When you install Warlords over that nothing happens since the install will just add more files to run Warlords - however the uninstaller doesn't know that and will remove the whole thing - killing BtS in the meantime 
It could have been solved better, I agree

It could have been solved better, I agree



I get a portrait of one of the players with a red background. Screenshots enclosed.