and quite a few were undertaken (but no RCTs), so they certainly didn't try to block it...unfortunately, the results showed no benefit over not taking the drug combo...and there are always concerns for cardiac arrhythmias with HCQ, which go back many years before COVID-19.
It's unfortunate that really effective and well designed drugs, like Paxlovid, can take a long time to develop...thankfully, we got it early enough to have a positive effect.