Something to note about Omaha, Nebraska is that it is within the second Congressional District, a swing district that could go for Biden. It already went for Obama in 2008 and the areas has been trending Democratic so it's not impossible. Personally, I think Biden will get the district, but you never know.
This is a smarter call than people think. Trump isn't campaigning in Maine likely because he's expecting to win the second congressional district there and the rest of Maine is likely too hard to pull. If he were to win the 2nd Congressional District in Nebraska and Maine, he can then keep all of the states except Michigan and Pennsylvania and then grab either Wisconsin or Minnesota for 270 electoral votes, giving him an electoral college majority needed for re-election.
That said, nice to see him hitting Pennsylvania, Wisconsin, and Michigan next week. Hopefully Minnesota is next, do a double or even triple rally.