How did the four-year cycle theory come about?

13-year bull market

17-year bull market

21-year bull market

While the years 12, 16, and 20 were actually just preparations for the bull market, similarly:

It is very likely that a major bull market will occur in 25, and additionally, from the perspective of market conditions, the overall market growth in 24 is not very ideal, with only a few cryptocurrencies like BTC reaching new highs, while most are still below the previous bull market peaks. Generally, a bull market is unlikely to last for 3 years, so a major bull market is highly likely to occur in 25.