I would note that not only do you need to acquire a lot of property on straight lines, you need to do so while resolving to not benefit anywhere between your start and end points.

Non-stop is an important element of a truly fast train. Firstly because you don't want to be constantly stopping and starting, but also because you don't want to detour your route through a dozen cities which aren't conveniently on a straight-line route to your destination.

So if you want to make a train run as fast as possible between Boston, NYC and DC, you're telling Connecticut, New Jersey, Pennsylvania, Maryland, and maybe Delaware, "Hey, we want to take a big chunk of your land for our project, and no, we don't want our super-fast trains to stop at any of your cities, and we can't even run a slower train because making the tracks actually go through the right parts of your cities would slow down our fast trains too much."

Have fun with your negotiations!