Really? Then why do governments historically go to war so frequently, and often for trivial matters like family honour of the king, or to intervene in conflicts

Really? Then why do governments historically go to war so frequently, and often for trivial matters like family honour of the king, or to intervene in conflicts far away that could never reach the homeland? Tax is irrelevant, governments can just print whatever the shortfall is (and they do). Realistically, there are lots of incentives for governments to kill their own population. Beyond national security there's the standard reason of just making mistakes, and then avoiding admitting to having made them. It happens regularly throughout history. As for conspiracies, sure they can do that. Snowden revealed massive conspiracies that had lasted decades and involved thousands, maybe tens of thousands of people. Now we learned that the US government seems to have funded Chinese research that led to SARS-CoV-2 escaping into the wild. You might counter that these are the ones they failed to keep quiet, but they were kept quiet for a long time. Who knows how many more are out there. The discovery rate on conspiracies is certainly not 100%.