The Index in the picture is the Large Transaction Index which indicates the occurrence of large BTC transactions recorded on the Blockchain.
Based on this indicator, you can see that during the collapsing time of the BTC price (March 2020 and July 2021) the number of large Bitcoin transactions becomes less. When the number of large transactions got extremely few as you can see in the above two points of time, real uptrends then took place more strongly than ever.
This is explained by the regular accumulation behavior of whales. In a bear market, whales tend to purchase Bitcoin for a very long time and have to buy in very small volumes because the market liquidity level is low and the target of accumulated Bitcoin number of whales is very high.
Based on this Index, the large transaction number is getting less, meaning that a strong bull market will take place soon.