He knew a little about everything.
Yes, but "knowing a little" is not enough to solve all problems. For example, he knew enough to use ECDSA, but he didn't know for example that public keys can be compressed. He knew and wrote about decentralized mining, but he didn't know how to make it "good enough for production", so he didn't include that:
Satoshi, I figured it will take my modern core 2 duo about 20 hours of nonstop work to create ฿50.00! With older PCs it will take forever. People like to feel that they "own" something as soon as possible, is there a way to make the generation more divisible? So say, instead of making ฿50 every 20 hours, make ฿5 every 2 hours?
I thought about that but there wasn't a practical way to do smaller increments. The frequency of block generation is balanced between confirming transactions as fast as possible and the latency of the network.
The algorithm aims for an average of 6 blocks per hour. If it was 5 bc and 60 per hour, there would be 10 times as many blocks and the initial block download would take 10 times as long. It wouldn't work anyway because that would be only 1 minute average between blocks, too close to the broadcast latency when the network gets larger.
As you can see, he thought what will happen when the difficulty will be higher. But he didn't know how to "instead of making ฿50 every 20 hours, make ฿5 every 2 hours" in a decentralized way. That means knowing some topic and talking about it is something completely different than doing that in practice and turning ideas into code.