They believe the tech is currently powerful and may become super super powerful very soon, and powerful tools can help us and can hurt us. Nuclear fission can provide so much energy to power our society and kill millions of beings.

So, i think they're hopeful for the help and terrified of the harms and are maybe trying to slow down on the amplifier of those effects for now.

The entire essay is about stopping development until it can be made more safe, with specific ideas on how to do that.

The fact that he would suggest this despite preparing for an IPO is an even stronger signal that it's in good faith -- it will almost certainly delay or reduce the valuation of the IPO.