While it can be determined that the evolution of cryptography and cryptanalysis is a result of a high level of academic and scholarly progression, the ability to analyze codes and ciphers does not necessarily have to come from that level of scholarship. In fact, amateur cryptanalysts are fully capable of analyzing and deciphering codes without much experience or training. It is fully possible that any normal person is able to solve these simple codes through trial and error.
In order to explain why the development of frequency analysis was so complicated and challenging and why in contrast, solving these substitution ciphers are seemingly so easy and simple, I want to use a simple example, or in fact any invention that we use practically today. One of the earliest and most profound inventions in human history is the wheel. The wheel took about 300 years to develop, yet today it is one of the simplest mechanisms that all of humanity understands. Similarly, Thomas Edison's invention of the lightbulb took one thousand attempts to master, yet today it is manufactured at an insane rate along with thousands of other inventions that probably took weeks, months, and even years to develop. In just the same manner, the people that developed frequency analysis may have spent hours and days trying to come up with the essence of frequency analysis, yet those that practice today have it down with ease due to the length of time for which it has existed.
Throughout time since the creation of frequency analysis, the human race has advanced in knowledge and logic and has since made the profound the simple. For this reason, even the most basic and amateur cryptanalyst has the ability to effectively decipher a substitution cipher "on their own".