I can see it happening.

One day you don’t show up for training, someone asks where you are and somebody says “I think they are training at another facility or something”. Later that week a head honcho asks where you are and are told you are training at another facility. Not wanting to lose face in front of the troops they just nod and accept it. They ask an aid to find out what facility and to get the training results to the science team so they can integrate it. The aid goes crazy as either no one knows or they just say any information about personnel is classified. He puts in a lot of effort to get the right clearances and get the data, but is unable to do so. Every time his boss asks he doesn’t know so he gets chewed out. At some point someone figures out what happened, but its too late, if it comes out heads will roll. So they think whatever, come launch day we’ll just put in the backup and it’ll be fine. But Murphy strikes and the whole backup team gets measles, at least that’s the official version (in realty they all got chlamydia). So there’s no choice but to put you in. Through the grapevine the crew finds out and is ultra pissed, but no wanting to let humanity down they roll with it.

The astronaut selection program also isn’t very rigorous. Any dayworker that shows up, really. /s

I mean, realistically they are in quarantine leading up to the launch. Don’t want to scrub the launch because your astronaut is sick or injured.

Look, Steve was clamoring for a new biome and going to space was his only option. ;ط

Same. Cheers. 🍺😎