The question is not why you believe but why do you believe while others exposed to the same truths do not? So Answer Me: WHY, WHY, WHY?
This could asked about anything, and proves nothing.
I could ask why when hurricane Katrina was approaching New Orleans and the National Weather Service warned people to evacuate, why did thousands of people believe the warnings and flee the city, while thousands of others did not heed the warnings and stayed, some of which died in the storm?
Did the National Weather Service send out an "effectual call" to only those who believed and evacuated? Did they send out a different warning to those who stayed?
So, this question of yours proves nothing at all. People believe for their own reasons, people believe not for other reasons. Some people probably believed the warnings were exaggerated. Perhaps some had rode out several storms before and believed themselves safe. Maybe they thought "it can never happen to me". I had a friend when I was younger, I used to witness to him, but he was busy having fun and partying. One night he was in a vehicle with friends and they went off the road and collided with a tree. My friend and another passenger were killed. My friend was young and healthy, he probably believed he had many years to live, he probably thought nothing bad could ever happen to him. This is how some people are.
There is no such thing as an '"effectual call". This is circular reasoning. Those who hear the gospel and obey are said to have received the "effectual call", those who did not obey did not receive this "effectual call". This is just like the evolutionist's who say "the survival of the fittest". Tell me, do the fittest always survive? Or did many young, healthy people die in the earthquake in Haiti, while many older, unfit people survived? Do the fittest always survive in war? Or do many young, healthy, fit people die in war? But the evolutionists will say they did. So, this is a false argument, I am amazed anyone can fall for this nonsensical circular reasoning.