The top tier rate was that high to pay for WWII. The rate didn't go similarly high for Vietnam, Desert Storm/Shield, or Afghanistan/Iraq because we have played shell games to cover the cost, with the net result being huge national debt and the social security fund being low enough that it may not be able to continue full payments through my lifetime.

Wars cost money. Taxing the wealthiest the most keeps wealth in investments and productive companies while securing the lower and middle class to provide demand with their lower rates. If you want low taxes on the wealthy, avoid allowing a geopolitical situation in which war occurs, and don't enter into them unnecessarily.