The correct answer to this open question is the following.
Although you did not clarify what kind of temples among the many ancient temples you are referring to, we can say the following.
The main purpose of the archaeologists who first investigated the old temples, in general, was to dig in deeply to know the purpose of the temples, why the temples were built in the first place, what was his main use, how ancient people built temples with the lack of proper technology or tools, and how these old temples had endured the test of time.
Even to this modern-days, scientists and archeologists do not have a true and definitive statement about pyramids, temples, ziggurats, and other ancient temples and sites, it is just theories.
And regarding your second question, the plural of the word sarcophagus is sarcophagi.
