Yes they recruited from a few but how many Pakistanis joined them? Very few, in actual fact they didn't even come up into the top 15....As for your assertion that those countries which are more open to Wahabism have more fighters is also wrong on the most part. I've already gave the example of Pakistan but let's look at which countries most ISIS fighters come from;
http://time.com/4739488/isis-iraq-syria-tunisia-saudi-arabia-russia/
Tunisia; strongly secular and even allows the marriage of Muslim women to non-Muslim men.
Russia; hates terrorism of any so called Islamic variety, as it's Muslim regions such as Chechnya have ruthlessly destroyed takfiri groups.
Jordan; strongly anti-ISIS and a firm US ally. The nation itself is descended from the Banu Hashim so at default oppose current Saudi religious doctrine.
You should also look at this;
https://www.nber.org/digest/jun16/w22190.html
A research paper which states a correlation between a country with higher HDI and ISIS fighters. Look at Pakistan!
You should also look at this excellent link on where most ISIS fighters come from, Bosnia and Albania have more per capita......Pakistan has the lowest, again!
https://www.rferl.org/a/foreign-fighters-syria-iraq-is-isis-isil-infographic/26584940.html
Some more;
Like I told you, a lawless area combined with foreign funding is what we have.