I don't believe War sec. John Floyd caused the war. My guess is that events happened so fast that Sec John Buchanan Floyd - who would go on to be a Confederate general - didn't react quickly enough in anticipation of future events, and simply maintained the status quo.
As I recall, it was the policy of then president James Buchanan that these federal forts should remain under federal control. On December 3, 1860, he submitted his "Fourth Annual Message to Congress on the State of the Union." He says the following:
Then, in regard to the property of the United States in South Carolina. This has been purchased for a fair equivalent, "by the consent of the legislature of the State," "for the erection of forts, magazines, arsenals," etc., and over these the authority "to exercise exclusive legislation" has been expressly granted by the Constitution to Congress.
It is not believed that any attempt will be made to expel the United States from this property by force; but if in this I should prove to be mistaken, the officer in command of the forts has received orders to act strictly on the defensive. In such a contingency the responsibility for consequences would rightfully rest upon the heads of the assailants.
President Buchanan says that the property was purchased fairly from SC with the state's consent, and is now under US control. He orders that the forts be defended if attempts are made to expel federal forces; and says that any consequences from such attempts are the fault of the (secessionist) assailants.