Well, when you zoom out a bit, it’s not a stretch to say that both Apollo and Vietnam shared the same goal of countering the USSR.

The Vietnam War was us violating Vietnamese sovereignty and self-determination and losing.

…and why did the United States feel the need to do so?

Honestly, that coincidence was NOT lost on me.

Part of me finds it inappropriate to do the two things at once. Advancement in scientific knowledge being somewhat at odds with blowing up one of the oldest civilizations in the World.

Your life must pass by really slowly with a lot of waiting if you don’t do more than one thing at a time.

It's a game of priorities I guess when resources are limited. And no: I can't do everything, everywhere, all at once. Can you?

Big rocks in the pickle jar first. For you that includes wars when talking was working?