Your thinking like a western civilized Christian American, not a dyed in the wool islamic Jihadist where death and martyrdom for the moon god is paramount. They made a choice to die in place and take as many infidels out as possible.
I know all that but it just seems like they thought they weren’t going to be caught. I haven’t heard what the older brother was doing in the couple of days that passed after the bombing. Did he have a job or what? Or was he just hanging out out his local radical mosque?