The most historically accurate response is that "Recent military successes had established the U.S.'s ability to back up its threats."
Theodore Roosevelt believed in the principle of "speak softly and carry a big stick," which meant that he favored diplomacy and negotiation but also believed that the credible threat of military force could be an effective way to achieve foreign policy goals. The U.S. had experienced several military successes, which bolstered Roosevelt's confidence in using the threat of force as a tool for diplomacy, as it demonstrated America's growing military power and influence on the world stage. This approach allowed Roosevelt to navigate international relations while maintaining a balance between aggression and diplomacy.