1. It was simply a blunt piece of diplomacy designed to prevent Soviet interference in the Greek civil war, and had no relevance beyond said civil war
2. It was not an aggressive act, but just to defend democracy and freedom from Soviet expansion
3. Truman needed to demonise communism and the USSR in order to justify his aim of turning the USA into a global power
4. He wanted to provoke the Soviets
5. By creating an enemy in the Soviets he could make other states dependant on the USA militarily and economically, boosting the US economy
6. First step in establishing containment as US policy post WW2