The author thinks governments should keep funding the projects because of their unexpected consequences that do benefit most people. Her argument is about unexpected consequences, not intended ones. Also, we don’t know that anyone’s preventing governments from funding the programs.

The author’s conclusion isn’t about underestimating the benefits of funding space exploration. Instead, she concludes that because of their unexpected beneficial consequences, space exploration programs should continue to be funded.

We don’t know whether the goal of space exploration is practical or not. So even if (C) is true, it doesn’t underlie the argument that governments should keep funding space exploration.

Space exploration has, in the past, produced unintended (or unexpected) benefits. So the principle that governments should continue funding projects that have produced unintended benefits does underlie the argument that governments should continue funding space exploration.

We don’t know whether space exploration is an ambitious technological undertaking. Even if it is, the author says governments should continue funding it because of its unexpected consequences, not in order to advance the welfare of society.