It's also incredibly valuable that we're developing multiple competing solutions to the problem. This means the problem will get solved, one way or the other. I recall multiple prototypes and development projects to replace the shuttle with newer spaceplanes during it's run. NASA would invest a lot of money and research into one design, and then they hit a fundamental roadblock that killed the project. And they were back to square one... the shuttle. Until they had a new idea, and started again.
Additionally, two successful strategies will be far more helpful than one. Consider that when a space shuttle exploded, it shut down the entire US space program for a lengthy span (sometimes years) while everything was reevaluated, refit, and recertified. When we shut down the shuttle program, we no longer had a viable route to space except through Russia.
If we have two viable craft from two viable contractors to get to space, we're able to rely on a persistent strategy that can weather unexpected events or problems.
Additionally, two successful strategies will be far more helpful than one. Consider that when a space shuttle exploded, it shut down the entire US space program for a lengthy span (sometimes years) while everything was reevaluated, refit, and recertified. When we shut down the shuttle program, we no longer had a viable route to space except through Russia.
If we have two viable craft from two viable contractors to get to space, we're able to rely on a persistent strategy that can weather unexpected events or problems.