For this particular painting, Brueghel sent Rottenhammer his landscapes into which the latter inserted his figures.
For the record, regularly I omit huge landscapes which feature the biblical scene in a tiny corner of the canvas (not the case in this one). By now, that must amount to several dozen of them. I just don't see the point of them.
Landscapes evoke the beauty of nature, God’s creation, suggesting His presence in subtle ways. Many, many artists used landscapes as a backdrop for their biblical stories; before the 16th c. landscape though was never a subject matter. It was during the 17th c. that landscape became important, influenced also by political and religious changes, especially during the Dutch Golden Age. As an example, after the Netherlands gained independence from Spain, Dutch artists began to feature scenes of their own countryside in a show of national identity and pride.
It’s all part of the evolution of painting and changing taste, but one can still focus on the religious moment while admiring nature and the mastery of the artist.