Try and imagine the amount of capital required to make the gains occur during market hours without the giant gap up on the cash open. Thats the magic of the stock index futures. All these overnight gains on a small fraction of the daily volume.
By the way, this is not how bear markets end. This is a feel good rally heading into midterm elections.
Funny how the market didn't budge at all during RTH yesterday and went to the moon once Globex opened.
I imagine there are certain "rules" and also arbitrage/hedging which put constraints on index futures during the equity session.