Why did the court decide that the second bank of the united states was immune from taxation?

The Supreme Court held that the Supremacy Clause (Article VI, Clause 2), which elevates federal law above state law when the two are in conflict (and do notinvolve a right explicitly reserved to the states) protected the bank from being taxed by the State(s). Chief Justice John Marshall declared the states couldn'ttax the federal government. Case Citation:McCulloch v. Maryland, 17 US 316 (1819) 

Nonsense