Fund Managers & Last 10 mins of trading day

Hi Pat!
First of all I hope you are feeling better. Thank you for all you do sir!
My question is about the last 10mins of the trading day. I’ve noticed huge volume coming into a stock int he last few minutes of the trading day, sometimes even the last few seconds. I know you used to be a fund manager so I wonder what is going on here? Is this sort of action caused by fund managers loading up and trying to hide their activity? I’ve noticed this usually leads to the next day push if the stock price is at a pivotal point. Could you speak to what is happening behind the scenes from your experience and knowledge? (For example March 24th, the last few minuets or even last few seconds GOOGL and MSFT and lots of other stocks got that huge volume surge and push.)  Looking forward to you shedding some light onto this stealthy action.
Thank you Pat!