Why was Harry S. Truman a good president?

President Harry Truman, a Democrat, was a good president because he ended World War II, secured the prosperity of Western Europe after the war, and took important steps to strengthen America's national security apparatus.
His accomplishments in the above areas include:
Truman was responsible for ordering the drop of the atomic bombs that ended WWII. This could be positive or negative evidence, depending on one's perspective. Although critics maintained that the bombings were an extreme act, President Truman countered with:

. . . it was done to save 125,000 youngsters on the American side and 125,000 on the Japanese side from getting killed and that is what it did. It probably also saved a half million youngsters on both sides from being maimed for life.You must always remember that people forget, as you said in your column, that the bombing of Pearl Harbor was done while we were at peace with Japan and trying our best to negotiate a treaty with them.All you have to do is to go out and stand on the keel of the Battleship in Pearl Harbor with the 3,000 youngsters underneath it who had no chance whatever of saving their lives.

He also signed the United Nations charter and was instrumental in the creation of NATO. President Truman signed the United Nations charter in 1945, and the United States of America became the first nation to join the peace organization. The president was also instrumental in facilitating the creation of NATO in order to counteract Soviet and Communist expansion across the globe.
Truman recognized the state of Israel in 1948. Despite fears that American involvement would strengthen a Soviet-Arab alliance, President Truman signed a recognition statement in support of the new state. He was a strong supporter of the Jews; his actions allowed many of them to flee to Palestine after Nazi persecution of the Jews began in Germany. This is another action that can act as evidence for or against Truman's merit, depending on one's perspective on the Israeli-Palestinian conflict.
He also established the National Security Council, CIA, and NSA. In 1947, President Truman signed the National Security Act, which led to the formation of the Department of Defense (a consolidation of the Navy and War departments), the NSA, National Security Council, and the CIA. President Truman's National Security Act was one of the most important pieces of Cold War legislation passed in the years just after WWII.
Truman also signed the Displaced Persons Act in 1948. By signing this act, President Truman allowed hundreds of thousands of displaced Europeans to settle in the United States after the war.
https://learnodo-newtonic.com/harry-truman-accomplishments

https://www.archives.gov/education/lessons/us-israel

https://www.history.com/this-day-in-history/truman-signs-the-national-security-act