They can believe A and B and at the same time they don't want to cripple themselves. Your logic does not hold up.
Similar situation: nuclear race - everybody knew the risks, but making yourself armless does not help in any way. You need to make sure everyone is on the same page before you make yourself vulnerable in any way.
Similar situation: nuclear race - everybody knew the risks, but making yourself armless does not help in any way. You need to make sure everyone is on the same page before you make yourself vulnerable in any way.