God allows mankind to walk away.
For perhaps he therefore departed for a season, that thou shouldest receive him for ever; (Philemon 15 KJV)
In the world it has been said absence makes the heart grow fonder. Onesimus was a slave whom the Apostle Paul was speaking of who chose to depart for a season. However, he did return after God did a supernatural work inside his heart.
This same thing happens to many individuals today. Just like Onesimus, God allows them to walk away from the Truth and straight into the heat and fire of spiritual trouble of some sort. Sometimes it takes falling head first in a ditch for some hard hearted individuals to see their need for a Savior.
God knows that sometimes mankind will choose to go on about their life according to their own will rather than God’s will but at some point will be poked and prodded into perhaps recognizing and acknowledging a personal need for receiving God as his Savior, just as onesimus did.