why does somebody have to go and do that to innocent people

So that their shit religion would be in the news and in peoples' minds and in threads like this. Strictly for publicity. Then their liars start blabbing in those channels about how "It's not islam, islam is peace blah-blah-blah."
But the very point is that the channels of communication that put Islam in the media was opened up by the violent actors of Islam. They want those conduits because they want to be a primary subject of conversation.