Speculation

People expected a return from the most recently deceased and backwards through time. It seemed to be based mostly on emotional reasoning. Having those that died be tied directly back to those that lived through the cataclysm was the emotional buoyancy that kept them going.

In practical terms, these people were of little use in the rebuilding. On the contrary, most of the time was spent recounting what little had transpired since they had passed away. What this time period needed was people that had subsisted on very little, and those that would bootstrap the re-organizing of the society.

To that end, a 'framework' of people from the entirety of human history were brought back in relatively short order. This allowed for a cohesive and balanced approach to problems. Major literature could be produced in all dialects from the beginning, rather than a staggered approach, as speakers became available.

It also diversified the talent pool, as blacksmiths, miners and carpenters of ancient times didn't require the tools that their modern equivalents did. Major scientists from history also got a earlier resurrection, so the moderns survivors, with their over reliance on technology, weren't left to be totally ignorant about the world around them.