according to the reading, why did the attackers carry out their attack?

The attackers carried out their attack because they believed they were performing an act of religious jihad. Specifically, in the case of the Reading stabbing attack in 2020, the attacker Khairi Saadallah believed he was carrying out an extreme ideological cause, intending to kill as many people as possible in the name of violent jihad. The attack was described as carefully planned and executed with determination and precision. Saadallah shouted "Allahu Akbar" during the attack and believed he was acting in pursuit of his extreme ideology.