Why was Thomas Jefferson so opposed to Alexander Hamilton's plan for a National Bank?
Jefferson saw the National Bank as encouraging the exact opposite of his goal for the US to be an idyllic agricultural and mostly rural nation of farmers.
Hamilton was a man of commerce and business, and he knew that the new nation would need strong financial institutions to survive, industrialize, engage in world commerce, and grow. Jefferson idealized the rural, agricultural, farming life, and hoped the US could escape the troubles and wars of Europe by remaining less commercial and less urban in its development.
The plan for a National Bank was directly contrary to and threatened Jefferson's ideal, and so he opposed it.