Why are stock upgrades by analysts after their Bank did a block trade sale not seen as a conflict of interest? Or market manipulation?

I have only been investing since Jan 2021 but I have seen it dozens of times. A block trade sale then a couple weeks later that same bank suddenly gives it an upgrade.

I want this to be a general question but if an example is needed Goldman Sachs just did it with CPNG yesterday source below. But I have seen JPM and BAC do it too.

https://finance.yahoo.com/news/coupang-shares-gain-following-goldman-101748443.html