Re: I just would like to know....
Its quite possible they have some correct suspects and some wrong ones. There will be procedures followed, naturally, to make sure they've got the right suspects. I'm surprised about the women, though.
As for the OP's original questions, to add to many valid reasons posted, I would say part of the problem is
Not enough knowledge about Islam, and religious leaders (imams, etc) who are giving a negatively skewed interpretation of Jihad and misleading people.
Moderate muslims not intervening in their community masjids to make sure the imams are not haywire, and that extremist activity is not being propogated.
Muslims giving false tip-offs to authorities to incriminate someone they have a personal grudge against. More common than we would think, but its not surprising, since muslims simply do not know how to treat each other with respect.