Have they somehow confused Trump with Hillary and Bill Clinton?
Wendell Willkie, FDR's opponent in 1940, died during FDR's third term, but no one has accused FDR of causing his death. Likewise, Robert Taft, Eisenhower's opponent for the Republican nomination in 1952, died during Eisenhower's first term, but no one suspects Ike of causing his death.
Lincoln didn't try to have any of his 1860 or 1864 opponents killed.
If Biden does succeed in having Trump killed, it will be a first in US history.