"Almost everything came about very, very suddenly--get informed, please--it happened in only a few millions of years."

1. This is like saying that you played the same lottery numbers for 20 years, and when you finally won it happened all at once.

2.  The emergence of complex life "very suddenly" was not random -- it coincided with the accumulation of significant amounts of oxygen in the Earth's atmosphere.  This enabled the possibility of ATP production via a chemical reaction 18 times more efficient than without oxygen.

Where did the oxygen come from?  That's what all the bacteria had been doing for billions of years -- photosynthesizing and releasing oxygen, but that oxygen couldn't build up in the atmosphere until it had reacted with all the unoxidized sulfur and iron just lying around, and that took a long time.

The fact that complex life did not exist before conditions were appropriate is no surprise.

Gaining this knowledge required that humans learned a little chemistry and studied a lot of rocks, but it was worth the effort, no?