ISIS began in 1999 in the Middle East with Al-Zarqawi who created it. Over time, he showed allegiance to Osama bin Laden with the Taliban. With other groups forming and coming together with ISIS, ISIS has strengthened and has become more powerful. Another way that ISIS has become stronger and risen to power is through gaining more land by attacking the cities in the countries that they want to take over.
Also, ISIS recruits as many people as possible by promising them a sense of belonging. They will target lonely people who want to belong to a group and charm them into becoming a part of ISIS. Usually, these people are young and impressionable so they are easily swayed to join.