why did they want to kill him?
So that they can install Elizabeth on the English throne as a titular Queen.
Gunpowder Plot
Once the King and his Parliament were dead, the plotters intended to install Elizabeth on the English throne as a titular Queen.
who was king at the time of the gunpowder plot King James I what was this plot? It was a failed assassination attempt against King James I by a group of provincial English Catholics
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Gunpowder Plot [SEP] Plot
Once the King and his Parliament were dead, the plotters intended to install Elizabeth on the English throne as a titular Queen. The fate of her brothers, Henry and Charles, would be improvised; their role in state ceremonies was, as yet, uncertain. The plotters planned to use Henry Percy, 9th Earl of Northumberland, as Elizabeth's regent, but most likely never informed him of this.