Vulcan is not yet rated to fly National Security missions (needs at least a second successful launch), yet it already has 60% of these contracts going forward.

Why? Because there is confidence in the company and its ability to deliver based on past performance. It's not rocket science. (Pun not intended :) ...)

What do you define as "most base level"? It's a development project. When something is in development you still have lots of bugs to be ironed out. However it was quite successful, even given that. It reached orbital velocities the last launch, which is all that a regular rocket is expected to do. It did fail to do a in-space relight of its engines, which eliminates some usages, but if it was just launching a regular payload it could've done that. And the next launch is happening sometime next month.

They have certainly in the company.

Also, one thing I'm not seeing mentioned is that Congress did not give NASA enough money to pay for any of the initial human lander system contract bids. SpaceX lowered their bid to accommodate this.

One can look at Falcon 9 and Falcon Heavy and reasonably project that SpaceX is capable of overcoming the engineering challenges of Starship.

The dubious part is accomplishing that on the Artemis mission schedule.