First of all, it's spelled Tsar. and now for the answer, there were many events that led to overthrow the Tsar, for example, the working class was very tired of non-equal pay and very bad working conditions. (Trust me, Russians have a very low standard.) This lead to the rise of opposing leaders, that are a bit nicer towards the working class such as the provisional government, and the communist party leader, Lenin.
Robert Kennedy was attorney general during his brother John F. Kennedy's administration.
As attorney general, he fought organized crime and was a key supporter of the Civil Rights Movement.
In 1953 Kennedy became an advisor to the Senate Subcommittee on Investigations under Senator Joseph McCarthy. Kennedy left the position just six months later, objecting to McCarthy’s unjust investigative tactics.
In 1960 Kennedy managed brother John’s presidential campaign. When JFK was elected, Robert was made U.S. attorney general and became one of JFK’s closest cabinet advisors. When JFK was assassinated in 1963, Robert resigned as attorney general the following September and announced his intent to run for a senate seat.
In 1968 Kennedy ran against Eugene McCarthy in the presidential election primaries. On June 5, 1968, following his victory speech at the California Democratic Primary at the Ambassador Hotel in Los Angeles, Kennedy was shot several times by gunman Sirhan Sirhan. He died the next day at age 42, his promising presidential administration over before it began.