There are several reasons why some people believe that Lewis was murdered. First, the room where Lewis died was locked from the inside, and there were no signs of forced entry. Second, the razor that Lewis supposedly used to cut his throat was found on the floor, away from his body. Third, there were several witnesses who testified that Lewis was in good spirits in the days leading up to his death.
Some historians believe that Lewis was killed by political enemies. Lewis had many enemies, both personal and political. He was particularly unpopular with some members of the government, who felt that he had failed in his mission to explore the Louisiana Territory. Others believe that Lewis was killed by a romantic rival. Lewis was known to be a womanizer, and he may have angered someone by having an affair with their wife or lover.
Ultimately, the mystery surrounding Meriwether Lewis's death may never be solved. However, the various theories about his death continue to fascinate historians and the general public alike.