According to creationism the fossils would have been caused by the Flood.
He didn't because the creation story does not mention fossils. Its author was not stupid but could have had no inkling of fossils or geological and astronomical processes and scales.
I suppose the Bronze Age scribe who did write it may have seen fossils as there is a lot of limestone in the Middle East, but would have not known how they formed or arrived in the rock.
Friends who visited Poitiers Cathedral on holiday told me they were intrigued to see a Mediaeval grave-slab whose effigy, a knight in armour, was resting his feet not on the usual dog but an in-situ ammonite! The Mediaeval sculptor could have no more more scientific knowledge than that Biblical author, but was evidently so intrigued that he carefully used it within the art-work! My friends looked around and found a number of other ammonites, still in their bedrock, used as decorative building details. If anything such people assumed God put them there for fun!
The sad aspect of creationism is that it so demeans the Biblical writer's and reader's intelligence, and ultimately their own god; whereas the more we learn about the universe and its natural contents - including fossils - the greater and more sublime we see it all is.
When God realized he didn't want to play with dinosaurs anymore, he threw down a meteor and started from scratch. So what happened before the Bible is non-existent, cuz God started over.
To confuse people and make them believe in evolution. But he didn't do it in the creation story. That happened much later when he decided to kill off all the dinosaurs because they got too big for the planet to sustain them with global warming and not enough plants to feed them. Boy, are we in big trouble!
Oh get real! Everyone knows we hadn't evolved yet! We just teensy tiny little monkey creatures hiding in the undergrowth...