Elizabeth's cousin Lady Jane Grey was forced to marry Guildford Dudley, then forced by her father-in-law to claim the throne of England, leading to her execution when Mary I took the throne
Mary married King Philip II of Spain, which dragged Mary into disastrous wars against France and led to rebellions from people fearful of Philip seizing control of England
Edward VI became a devout Protestant, Mary I restored Catholicism to England, and Elizabeth initially attempted to forge a 'middle way' for religion in England
Elizabeth ended the war that Queen Mary and King Philip had begun with France, sought to build a positive relationship with Catholic Spain but this did not last
Elizabeth provided support to Protestant rebels in the Netherlands against Catholic Philip's control, which angered Philip and led to him sending the Spanish Armada to invade England in 1588
The Church taught that women were weaker than men as Eve had been tempted by the snake in the Garden of Eden. Power was traditionally held by men and people were used to being ruled by kings.
Elizabeth was often underestimated owing to her gender. As many believed she would be weak this increased the risk of invasion. Furthermore were Elizabeth to marry her power would go to her husband
elizabeth was seen to be illegimate by catholics

Henry VIII had divorced his first wife Catherine of Aragon to marry Anne Boleyn. In order to do this Henry had to break from the Catholic church in order to secure a divorce as this was against Catholic teachings. As a consequence many Catholics saw the marriage between Anne and Henry as invalid as Catherine of Aragon was still alive
As Catholics believed Elizabeth was illegitimate many wanted to replace her with a legitimate heir to the throne, this was in the form of Mary Queen of Scots.