Why was it such a huge mistake for Civil War generals to adhere to Napoleon Bonaparte's famous military?

It was a huge mistake because they were still so imbibed of Napoleon's strategical and tactical principles to not realize the great evolution the new technologies (rifled weaponry, railroads etc.) in being would have brought about both in tactics and strategy.

Only after the early stage of war they became aware that those principles had become obsolete and they slowly provided to change their minds but at the cost of huge losses in terms of men and means.