When a messenger speaks to a large crowd directly in the name of God, the impact is profound. For the Israelites gathered together, this direct address was a completely new experience [ביאור שטיינזלץ]. Hearing the sharp words of rebuke, the crowd broke down in tears.
The primary approach among commentators is that this intense emotional response was born from a deep sense of guilt and a clear recognition of their own wrongdoing. The people suddenly realized the foolishness of their actions. They openly admitted their faults and were overwhelmed by a feeling of helplessness, knowing they had failed to fulfill what was required of them [מלבי״ם, אברבנאל, ביאור שטיינזלץ].
However, this deep awareness and confession did not lead to practical change. Instead of fully correcting their behavior, the Israelites simply cried and offered sacrifices to God. Yet, even though their repentance was not complete in action, their genuine sense of surrender and their tears were still valued and received positively by Him [חומת אנך].