We might agree on a few points but trying to clarify that the murder wasn't a terrorist attack, that it was just "unplanned murder with a vehicle", makes me want to re-examine my opinions on the points where we agree.
The murderer may not have woken up that morning and pulled out a binder full of detailed notes on vehicular murder from under his bed, but he did not accidentally drive into that crowd of people. When he got into the car and plowed into that group, he did so because he stopped regarding them as fellow human beings, because he disagreed with their opinions on some issues, and because he hated them.
It was an act of terrorism, identical in purpose and outcome to other acts of terrorism in the UK.
You make it sound like the facts are known and the arrested has already been convicted. I have every suspicion that the events happened as you describe with murderous intent, but will wait on the criminal court's decision.
EDIT: I struggled to figure out how to include that the horrific events happened in less than a minute.