3rd teen arrested in foiled attack on now-canceled Taylor Swift shows in Austria

A planned terror attack at a Taylor Swift concert in Vienna was thwarted by Austrian authorities. A suspect was arrested, who had contact with the main planner and pledged allegiance to ISIS. Several concerts were canceled due to the plot, which aimed to cause mass casualties inspired by extremist groups like ISIS and Al Qaeda.

What was the intention of the suspects according to the plot?

Which extremist groups inspired the suspects in their planning?