Your question was whether bond holders who sold bonds to the Fed would have been able to sell those bonds had the Fed not bought them as part of its 4 trillion

Your question was whether bond holders who sold bonds to the Fed would have been able to sell those bonds had the Fed not bought them as part of its 4 trillion bond purchasing program. And the answer is that, considering the average daily trading volume in the US bond market, which is a little under 1 trillion, whatever liquidity the 4 trillion Fed program provided, it couldn't possibly have made a big difference. Now you're making a different claim which is that the Fed inflated asset prices by pumping up the bond market. Yes, bond purchases by the Fed will tend to make bond prices increase, but your math is nonsense. Buying 9% of the supply of something doesn't mean the price will go up by 9%. This is not how prices work. Whether the Fed pumped up the bond market is an empirical question, which should be answered by looking at bond prices and seeing if they went up during 2020. So where's the data showing that bond prices were pumped up?