If we accept this is an act of 'Islamic terrorism' we must also say that any murder or assault committed by someone who happens to be a Muslim is 'Inspired by Isis or Islam' Isis will always claim any murder by a Muslim as 'By One of our soldiers '
This guy had a long history of crime which was becoming increasingly violent. He has been recorded as having mental health problems which include expressing a strong desire to kill people.
He drove his car straight into a group of tourists sightseeing on Westminster Bridge, he can have had no idea if they were Muslim, Christian, Hindu or of no faith. Then he continued on to drive into the gates of the House of Commons where he stabbed a police officer who tried to stop him. At that point it became inevitable that he would be shot.
He had possibly realised what he had done at that point and thought 'Suicide by Cop' was the only way out.
As Mikey said the association with Isis came after he had decided he wanted to kill people. He probably was looking for a way to justify his desire to murder people!
I am as appalled by this act of cowardly cold blooded murder as any of you, but I see it as a criminal act by a man who was mentally unstable with delusions of mass murder rather than a politically inspired act of terrorism.