One of the big reasons is that mrna is also much easier to manufacture than proteins. If I wanted to, I could pay for a arbitrary mrna sequence delivered to be

One of the big reasons is that mrna is also much easier to manufacture than proteins. If I wanted to, I could pay for a arbitrary mrna sequence delivered to be within the week. Its basically been commoditized. Conversely, getting a protein at scale requires the engineering of an organism to synthesise the protein of interest. This results in increased delay in manufacture.