No deep analysis on this one. I just think it's a crazy good deal to be able to buy stock of the biggest corporations which lead humanity technological progress, have huge political influence and even at today profit levels return 3-4% per year (in reality much more as a lot of money is invested in research/new projects which are going to be profitable in the future). I think Apple/Amazon/Alphabet/MSFT etc are going make even more in the future and current price is a steal, especially considering those are highly liquid assets with 0 cost of maintenance.
Because another way to read the situation is that stocks are simply the asset of last resort. In a world with no interest, you can't park money in bonds (or CD's etc.) so you've basically got stocks, real-estate and commodities left as options.
Large-scale asset managers are not going to park billions of dollars under the mattress, so basically it has to go to stocks.