It's not just radical islam. Just see some very recent incidents in the US. It's dehumanization and fanaticism that's the problem.
Also, seems to now be confirmation that the truck driver was shooting as he was driving.
It's not just radical Islam, but the vast amount of it is. How is dehumanization the problem? Please explain. Who is being dehumanized??
Radical Islam has been around for years though, the question as to why it is attracting people, and how to stop it, is demonstrably more complicated than simply denouncing the ideology.