Linked from
The 12 pages that link to Execution of Charles I of England, each with the reason it gives.
Oliver CromwellRelated: Cromwell supported the regicide, which ended the monarchy for eleven years.
Commonwealth of EnglandRelated: The regicide cleared the way for Parliament to abolish the monarchy.
Pride's PurgeRelated: The reduced Commons authorized the king's execution after the purge.
Second English Civil WarRelated: It followed the war and ended the king’s personal rule.
Stuart RestorationRelated: The execution had abolished the monarchy that returned in 1660.