Some interesting economic forecasts. For those familiar with Kondratiev’s Economic Cycles and Strauss / Howe generational theory - The Fourth Turning, this would be a continuation of these discussions
https://realinvestmentadvice.com/natural-time-cycles-a-dow-forecast-for-2018-2020/
In any random series, there will be some periods with higher correlations than others. These aren't cycles, these are random events. So, of course, there will be some apparent 'cycles' in a century of stock market data. In reality, though, these 'cycles' simply do not predict the future.
You seem uninformed about what really drives the markets. The markets move either up or down on corporate earnings. End of statement!
Earnings of course can be impacted by events worldwide or even to an extent local depending on the company. If people are buying stuff then companies do well their earnings increase people see this and buy the stock making the stock market go up. When people see bad things happening locally or around the world they become frightened and they pull back on their spending. This causes corporations to sell less of their products, whether it be hard products or services. The result is earnings sink which causes the stock to sell off.
Trying to look in the past to determine what will happen in the future is just about the most ignorant way anyone could ever find to choose a plan of investment.