Decisive.
I'm not a fanatic about vaccines either way, so I don't follow the news closely. I feel that my vaccines will protect me adequately as long as I'm not stupid. If I'm stupid, then the consequences are my fault.
To the extent that I followed the news I didn't see any large companies mandating vaccines until the administration announced its plan to mandate them. If someone gave me 4 to 1 odds I would bet that the mandate never takes effect, i.e. that the administration backs down or the courts force them to back down. Legalities aside, IMHO the danger to uncompromised vaccinated people is not great enough at this point to justify a mandate. We take greater risks riding in passenger cars. The risk of the vaccine itself is unknown. I personally believe that risk is quite low and getting lower all the time, but nobody knows for sure. If I had a healthy 2-year-old child I would think long and hard about the balance of risks before choosing an mRNA vaccine. Minimax logic says you should choose a low probability of bounded harm when the other option is an even lower probability of unknown and therefore unbounded harm. But nobody decides that way. We all decide based on our feelings.
Time will tell whether the United or the Delta response was better for the company or for the employees. I don't claim to be able to predict that answer. Don't believe anyone who professes certainty.
Google, Microsoft, and Tyson foods are just a few of the very large and very well-known companies that mandated vaccines before Biden's mandate. There are many more companies you've heard of and use their products/services that mandated vaccines before Biden did.