It was purposefully made trivial to increasing degrees. Read the first section again closely.

Think of it like this, if I tell you I multiplied a secret number by anything between 1,000,000,000,000,000,000 and 999,999,999,999,999,999,999, then it’s going to be hard to figure out what the number is. But if I make it known that I used a number between 10 and 100, you’ll get it very quickly.

This was a cryptography puzzle built with very low entropy (small numbers) and gradually increasing to extremely high entropy. Only the very, very low entropy addresses have been found.