why do you think the development of agriculture occurred around the same time in several diffrent places?​

Technically, agriculture was not developed at the same time in different places; different cultures developed it over a period of several thousands of years. But all occurrences that we know of took place after the end of the Pleistocene, when Earth’s biomass was shrinking. Prior to that, everyone could get by with hunting and gathering, presumably because there was more natural food available.

Agriculture most frequently developed in regions that we know of as being arid or desert, and these regions might have been more fertile thousands of years prior. Groups of people may have developed agriculture in response to the wild food sources becoming more sparse with climate change.