Why did the Interregnum last only from 1649 till 1660?

Possible reasons for the short tenure could include:

- Parliament planned to disband the New Model Army which angered them, and forced them to take action

- Cromwell’s unprecedented introduction of the Major Generals angered all classes of people.

- Richard Cromwell’s political ineptitude and hostility to the Army made him unworkable for the Army grandees.

- The Rump became more conservative, forcing Cromwell to dissolve them forcefully.

- Much of the Rump Parliament refused to be involved in the Regicide.

- Levellers were influential pamphleteers of liberty and loud opponents of Cromwell.

- Quakers were religious radicals and served as a point of disagreement between lenient Cromwell and Conservative parliament.

- Fifth Monarchists influenced Cromwell and were a radical vocal minority in the Nominated Assembly.

- Wars in Ireland and Scotland meant increased taxation which resulted in resentment.

- Poor harvests in 1649 and 1650 pushed farmers to poverty, which reflected into resentment.

- The Anglo Dutch 1652-54 war put a halt to trade and meant increased taxation.