Families tend to move in groups. That’s true whether the journey is one of several thousand miles across an ocean or a few hundred miles across a small mountain. When they move in groups, they tend to move over time–not all at once on one day.
Who was the first one to arrive in the area? Who came later? The first migrants tend to be single men–but not always. They send word back to the “home folks” and more decide to make the journey once the earlier immigrant or immigrants have settled.
Don’t assume your ancestral couple was the “first set” to arrive. There may have been an earlier immigrant, perhaps a brother, cousin, or neighbor. Even if they were the “first, they possibly encouraged others to follow them. It’s uncommon for people to migrate in complete isolation–but it does happen.
One of my ancestral families were natives of Maryland who moved to Kentucky as children around the turn of the 19th century. Between then and the 1870s, they moved as adults from Bourbon County, Kentucky, into central Indiana, and eventually into Hancock County, Illinois, and Linn County, Iowa. They did not move all on one day or even in one year, but eventually they followed each other.
My Ostfriesen immigrants did the same thing in the 1860s into Hancock and Adams County, Illinois.
Look for those other relatives, neighbors, etc. who might have traveled with them. And remember–it wasn’t always non-English speakers who traveled together over time. Many did it. Social bonds apply to all.