Why is a really good question. I have my theories.
1) Politics - they wanted every excuse to disrupt Trump’s presidency, and an off-the-shelf treatment would undermine that effort. These leftists are really disgustingly Machiavellian.
2) Money & Technology - there is no money to be made giving out cheap generic drugs, vitamins and minerals. They wanted the billions of dollars to subsidize the mRNA technology platforms not just for Covid but for potentially other diseases. Of course, they could have invested that money in mRNA and still allowed the generic medicines but see #1. But, if there were cheap generic treatments that would block the cell receptors and prevent viral replication, they would never have been able to enroll the 100,000+ people in the vaccine clinical trials, thus delaying the deployment of mRNA technology. Everyone would have just taken the $5 pills.
Why?
Perhaps because the FDA has legal stipulations it must meet prior to being able to grant an EUA authorization for a vaccine. One of those legal requirements is that there cannot be any affective available and approved alternative. HCQ met all three of those it is criminalThat they barred people from having access to HCQ just so the FDA could allow the vaccine to be used under the emergency use authorization.