There have been continuous protests and battle against him and he refused to resign. Even last week's military takes over and days of protests never made him resign. But now all of a sudden he has resigned and a letter from Mugabe says that this decision was voluntary and he made wants to have a smooth transition of power.
The people of Zimbabwe have started celebrating in the streets as he stepped down. As per the constitution, the current Vice President, Mr.Phelekezela Mphoko should take over the presidency. UK Prime Minister Theresa May said Mr. Mugabe's resignation provides Zimbabwe with an opportunity to make a new path and travel on a new lane."