«إِظْهَارُ الرَّغْبَةِ فِي وُقُوعِهِ»
Showing a strong desire that the event occur.
A desired result can be pictured as already attained though it remains unrealized. In such cases the form expresses a psychological or rhetorical stance, not a historical report about an event that actually happened.
This explanation requires a relevant context of request, aspiration or purposeful effort. Not every past form in a conditional clause expresses desire.