It is important to remember that Leonardo was a polymath, deeply interested in various disciplines including painting, sculpture, architecture, science, engineering, and anatomy. He viewed art as a powerful tool for understanding and representing the world, regardless of the medium.
While Leonardo undoubtedly admired the power of painting, he also respected poetry and other art forms. He recognized the unique strengths and capabilities of each discipline. For instance, in his writings, he praised the power of words to evoke emotions and convey ideas.
It's likely that Leonardo saw the different art forms as complementary rather than competitive, each capable of achieving different effects and offering different perspectives.
It's important to be careful about attributing specific beliefs to historical figures without evidence. In this case, the claim that Leonardo believed painting was superior to poetry is likely a misconception.