does not mention anyone witnessing miracles involving Muhammad, either his flying to Jerusalem from Mecca, and from there to heaven, or the miracle of the angel Gabriel talking to Muhammad and revealing all the verses of the Qur'an to him. So people who died for Muhammad, like in ancient battles between Muslims and Arab pagans, they did not die for the miracles they saw Muhammad do, they did not see miracles, they died because they thought Muhammad was a very credible prophet, he was clearly a very charismatic man. Kind of like Jim Jones, though maybe not as psychopathic. People died for Jim Jones too.
The man who killed himself and others in Manchester, was clearly misled by ISIS propaganda, they taught him to hate all non-Muslims and be ready to kill them, those ISIS people are very misled, they believe the propaganda that all non-Muslims are very evil and deserve to die. It is sad, the members of ISIS will likely die still unsaved. Though I expect that after their resurrection many will be converted, repent of their sins and become saved. But now they are dangerous and we have to fight them. It is like Paul, he was a dangerous persecutor of Christians, until he became saved, when Jesus appeared and spoke to him, on the road to Damascus.