On March 25, market observers noted that the Bitcoin network recently experienced a rare two-block reorganization event. The chain from the largest mining pool, Foundry USA, temporarily overwrote blocks from Antpool and ViaBTC. This event is not merely a minor technical occurrence but also a clear reflection of the current trend towards hashrate centralization within the Bitcoin mining industry and the potential risks against the backdrop of a contracting sector.

The incident occurred when Antpool and Foundry USA each mined valid blocks within a 12-second interval, causing a brief network split. Subsequently, Foundry USA consecutively mined blocks 941,883 to 941,886, giving its chain a significantly higher total proof-of-work, which led the network to reorganize onto the Foundry USA version. The blocks from Antpool and ViaBTC were orphaned. Analysts compared this situation to two checkout lanes in a store, where the faster lane attracts everyone, causing the slower lane to be abandoned, leaving the miners who worked on the orphaned blocks without a reward. It is important to note that transactions within the orphaned blocks are returned to the mempool and will be confirmed in subsequent blocks, so no funds are lost; however, for the affected miners, it represents a direct loss of revenue.

This highlighting of hashrate concentration coincides with a contraction period for the mining industry. On Saturday, the Bitcoin mining difficulty was adjusted downward by 7.76%, representing the second-largest decrease of the year. The network's hashrate has retreated from its record high of over 1 ZettaHash in January 2025 to approximately 920 ExaHash. Analysis suggests the core reason for this change is the current Bitcoin price being significantly below the industry's average production cost, forcing small and medium-sized miners to exit the market. Each operator that shuts down further consolidates hashrate into the hands of a few large mining pools, creating a "the strong get stronger" cycle. This dynamic is the underlying logic that enabled the rapid two-block reorganization to occur.

Although a two-block reorganization does not pose a threat to Bitcoin's overall security—the network quickly restored consensus within minutes according to the "longest chain wins" rule—analysts warn of the long-term risks associated with hashrate centralization. As hashrate becomes concentrated among fewer pools, the probability of a single pool mining multiple consecutive blocks increases significantly. When two major pools discover blocks almost simultaneously, the likelihood of competing chains forming rises. While this does not break consensus, it can impact network efficiency and the fairness of reward distribution among miners. In summary, this rare two-block reorganization is a direct signal of increasing concentration within the Bitcoin mining industry. In the short term, the event does not alter Bitcoin's operational logic, and the network continues to function normally. However, long-term, if industry cost pressures persist and the trend of hashrate centralization continues unabated, it could further exacerbate the Matthew Effect within the sector, potentially harming the diversity of the mining ecosystem. Market participants are advised to continuously monitor changes in hashrate distribution and the impact of industry cost adjustments on the mining landscape.