JPII kissed the Koran because his religion was the Religion of Ecumenism which does not come from God.
That’s the best explanation I’ve heard. I remember the first time I saw the pic of JPII kissing the Koran. My eyes bugged out of my head. I was more naive then, but I knew that Christians must never give legitimacy to false religions. That hurts everyone. Less mature Christians get the idea that other religions are an acceptable option. The practitioners of false religions are led to believe we approve of their fatal error. In the case of Islam, they can even surmise we condone their slaughter of non-Muslims, etc.
I suppose, it being JPII, no one with any authority or influence ever questioned him on it. That would be a shame. We all need lovingly imparted edification from time to time. For some, it’s harder to come by than for others.