God Himself is an all-consuming fire although this fire only consumes one thing . . . sin.  It's not that God cannot stand to be in the presence of sin, it's sin that cannot stand in the presence of God, that is why God is holding off coming to this world as long as He can to save as many as he can.  With Israel this was no different, God put in place boundaries because He wanted to protect them, just like us today.

Search for Real Mt. Saini:  https://youtu.be/0njUOfgh1kI