What are the causes of the blurring of insight that prevents a person from distinguishing between truth and falsehood during times of tribulation, despite their eagerness for acts of obedience and worship, and does drawing closer to Allah not provide immunity from tribulations?

"Insight is a light that Allah casts into the heart, by which one perceives the truth of what the Messengers have conveyed. Its meaning is the realization of benefit and harm from something, or that which dispels confusion. The greatest means of attaining insight are piety towards Allah, knowledge of Him, His Names, and Attributes, zeal for Allah's sacred limits, and asking Allah for insight. Its opposite is committing sins, ignorance, heedlessness of the remembrance of Allah, and self-admiration. Allah's divine grace and guidance are the foundation for attaining insight."