It's simple because Sunoo was his competition and the producers wouldn't risk not debuting Sn knowing that he was the most popular in I-land since day 1 and probably has the biggest fanbase pre-debut. He only didn't rank high on the final because his fans got complacent and voted for their other picks since they thought that many will vote for him (but it seems that many of his fans thought the same). It was clear since Part 2 of I-land that 6 boys will debut by global votes and 1 from the producer's pick. If any member aside from Heeseung and Sunoo is his competition I bet the producers would've picked him.
If we get their average rank throughout Part 2 still Sunoo is higher than K.
We can argue about sunoo vs k but its not worth it. K was done dirty imo and thats what im sticking with. Yes i watched all of i-land and yes i took part in voting. Therefore how i feel is valid. However for the sake of not having a headache i will refrain from saying my thoughts.