What are they "actually" "aiming" by doing all these crazy worse things?
What do terrorists normally aim for by doing terrorism and murder? To spread fear and promote their political goals. Their goals being an extreme form of fundamental Islam. Isis go to extreme lengths of brutalism and that's how they get the media hits and their terrorism spread around the world for them and for free.
What they are doing is not Islamic. So... I asked.
It's not Islamic in
your opinion but it is in theirs. You can interpret the Qur'an and most other religious texts to suit your own agenda and that's what they do. I can find plenty of quotes from the Abrahamic religions that sanction murder etc but these books belong in the past and have no place in modern society.
While I agree with you with the part that the Quran is being interpreted in a way to serve their agenda, I disagree with the rest.
As someone who read and took time to read and understand 3 of the holy books, I'll try to simplify things and show you where the confusion comes from and how these people in doctrine other people
The Quran is split in two main part, Madani and Maqi, One part is mainly about how Islam works, how you should treat others (familly and outsiders), treat animals the environement... and how to be a good muslim in general (no killing, no theft, respect your parents especially your mothers, your wifes how to treat your children, never be offensive or insults others......), and the other part is about the fight back and defend once self against the infidels that been trying and chasing Mohamed all the time from Mecca and to Medine and what's not and when your read this part you see that you cannot take anything out of context, for example you have Sourate that explains how you should be firm against the enemy fight till the end and a few verse later it tells forbids you from killing anyone who surrendered to never kill women and children to threat prisoners well and so on and so forth.
The context is clear, yet, to serve once agenda it is brought out of context, not to mention that the Quran is written in 7 century arabic which is more complex than the simplified arabic used nowadays, which means that for someone to claim explaining the Quran they need to have advanced studies being it in language but also in historic events and what's not, yet ISIS people have none of those, in fact many of them doesn't even speak Arabic......