Why did the Hittite Empire collapse?

Google is your friend:

Type the keywords "Hittite Empire" in Google or Wikipedia and your answer will appear.

Or better yet. Read the assigned history textbook assigned by ones university professor or high school teacher.

When they realised that Hittite glue didn't bond very well when the temperature rose above 31c.

The very first day of summer that year, the whole continent experienced a mini heatwave and the empire collapsed within a matter of hours.

It was this major flaw that led to research into polymer based adhesives.

It wuz cuz they cou'n't walk like Egyptians . . .

After 1180 BC, amid general turmoil in the Levant associated with the sudden arrival of the Sea Peoples, the kingdom disintegrated into several independent "Neo-Hittite" city-states, some of which survived until as late as the 8th century BC