Sadly, mankind’s capacity for evil has remained consistently high throughout time. What has changed is population movement and instant worldwide communication giving conflict a far greater reach than ever before.
There is a grim cycle to these stories. First there is the “magnificent response” of the emergency services, then “communities coming together” then cries of “They shall not win”, then criticism of the security services who “could have done more” then dark suggestions that “others were involved” then funerals representing a “celebration of good not evil”. Rewind for the next one.
It seems that it was a suicide bomber, that is the preferred modus operandi of Middle Eastern terrorism, beyond that we will have to wait.
There will be justified scrutiny of the religious, ethnic, cultural, political and community context of this attack. But sometimes we can seek rational explanations where there are none. Where individuals, or small groups, have mentally moved to a position where they do something, “because they can".