Divine mercy despite human shortcomings

فَإِذَا رَكِبُوا۟ فِى ٱلْفُلْكِ دَعَوُا۟ ٱللَّهَ مُخْلِصِينَ لَهُ ٱلدِّينَ فَلَمَّا نَجَّىٰهُمْ إِلَى ٱلْبَرِّ إِذَا هُمْ يُشْرِكُونَ

And when they board a ship, they supplicate Allāh, sincere to Him in religion [i.e., faith and hope]. But when He delivers them to the land, at once they associate others with Him