Well, it
was luck, in this case. The cave paintings at Lascaux cave were discovered entirely by accident, by a dog (and its pet teenagers).
http://www.thinkfinity.org/2011-09-12_Lascaux-cave-paintings
As for developing technologies so fast in such a short time.... once a break-through is made, such as the ability grasp objects and to make the mental connection between a sharp point and being able to kill one's prey...the next step is to use a sharp rock shard to sharpen a stick to make a spear, and then to fashion spear tips from the rocks themselves.
So, proto-humans, once they had transitioned from arboreal life to fully bipedal terrestrial life in the high-grassland savannahs of Africa, retaining binocular vision (as it proved beneficial to bipedal high-grass terrestrial survival), finding themselves with their hands free for uses other than climbing and brachiation, gradually began using them to pick up stuff, then fiddle around with stuff, then use stuff as weapons, then use stuff as tools. The brain had to have had an initial "insight factor" to get the ball rolling, so to speak, but once it did, the two things -- the fiddling and the brain development -- fed off each other. The emergence of any mutations that promoted better forms of this (such as a totally opposable thumb) were passed along in the genes due to the superiority of survival of those who possessed them.
And keep in mind that "so quickly" can mean tens- or hundreds of thousands of years, not "next week."
We stand on the shoulders of giants! We continue to have rapid advances in human technologies, and our genetics are probably subtly going along with these changes due to the level of survivability that our technologies give us (medical, in particular). Think about it...electricity "discovered".... sudden boom in technologies from crank-up phones, electric lights and radios, flight... to space flight, robotics, computers and high-speed Internet. My father, born in 1917, has witnessed almost the entire span of those technologies that occurred in the course of a mere 100 years.
I,m sorry, it is just when I hear the phrase "boy we were lucky" I shutter, I believe everything has a contributing factor by an action. Anyways I just find it odd that we developed technologies so fast in such a short time... almost surreal.