“His greatest victories were taking Vicksburg and his breakout of Chattanooga.”
He totally BUFFOONED Chattanooga. The breakout occurred IN SPITE OF GRANT. Had his orders been obeyed, it wouldn’t have happened.
Shiloh was another example of such bad leadership by Grant that he deserved to be fired.
https://www.grantunderfire.com/
https://www.grantunderfire.com/961/a-critique-of-the-history-channels-miniseries-on-ulysses-s-grant/
Grant’s military reputation is based on his memoirs, which were the primary source for many historians. But Grant either lied or grossly mis-remembered what happened. Contemporary accounts, and the orders he actually gave at the time, show he massively screwed up many battles.
Not all - he did have a few genuinely excellent moments. But his reputation was built on the book he wrote with Mark Twain, not what he actually did, thought, and tried to do during the war.
Yet Grant lost only one battle the entire war (Cold Harbor) and never made the same mistake twice.