The sudden ruin of a truly wicked individual, especially one responsible for the betrayal and murder of God's priests, creates a profound ripple effect. When those who strive to do good witness such a dramatic downfall, they experience a powerful, two-part reaction that is both spiritual and emotional.
First, the harsh reality of divine punishment inspires a deep sense of awe. The primary approach among commentators is that witnessing this justice directly strengthens their reverence for God. [אלשיך] explains that the death of the wicked is actually a massive act of divine kindness for the entire world. If a person could commit terrible atrocities and continue to live in peace, good people might question divine justice and eventually lose their faith. Removing the wicked is comparable to amputating a diseased limb to save the rest of the body from dying. Adding to this profound sense of awe, [מלבי״ם] notes that observers recognize God's exact and careful providence, as the punishment fits the crime perfectly, measure for measure.
Following this initial reverence, the emotional response shifts toward mockery of the fallen individual. [תורה תמימה] points out that this is a gradual process. The initial fear of strict divine justice eventually gives way to laughter. This laughter is aimed directly at a person whose religious devotion was completely superficial, nothing more than lip service, which is now fully exposed by his ruin. [רש״י] clarifies that this mockery is a sober realization of the consequences of poor choices. The righteous look at the fallen man and point out to one another the inevitable fate of anyone who actively chooses not to place his trust in God.