Because the army wanted to change the country to be the way they thought it should be and King Charles would have been dangerous to keep alive. Ironically, executing him was so unpopular that it probably ensured the return of the monarchy a little over a decade later.
...King Charles the 2nd...
The Cavalier King Charles Spaniel received its name from King Charles II.
Charles I was 5ft 4.
Charles pickney King Charles the 1st king Charles the 2nd
Charles William King died in 1888.
Charles Croker-King died in 1951.
Charles King Hall died in 1895.
Charles King-Turner died in 1972.
winsor
Charles King - academic - died in 1867-10.
king charles 1
Charles King - general - died on 1933-03-17.