There are many reasons for it one of the strongest is that by survey we see all the terrorists killed till now are muslims
I wouldn't go to the extent of saying that all the terrorists are Muslims. There are a lot of non-Muslim terrorist groups out there, such as the ETA of Spain and the ELN of Colombia. But when it comes to religion-based terrorism,
Muslim groups are involved in 99.99% of the incidents. Replying to your bold part. Why muslim groups are involved mostly in such incident ?
One thing which islam teaches is " Hurriyat " - " Freedom " ... God made u free man, so stay free and think free.
While West don't want humans to think free or do free. There is what clash starts. This was used by USA against Russia due to Oppression on Muslims in Chechania and the rise of Voice for freedom was picked by USA to destroy Russia, in which Afghans , Pakistani, Iranis are getting used by providing weapons.
Even if USA not gave them support , they will get freedom ( may be in 100 years but they will get bcoz of struggles they started ) , same like u can see in Gaza where small small groups are continously working against Israeli occupation on there lands. One day they will get freedom bcoz they decided not to surrender.
That is what Oppressor don't like , and that is why he gave them name " TERRORIST "
Because Islam is teaching not to accept Oppression , so obviously those who will raise there voice against Oppression are treated as Enemies. And Oppressor if used weapon then resistance too is force to use weapons. And that is what happening everywhere.
I hope u understand what i wrote.