Goerli was the last of three public testnets to run through a “dress rehearsal” of the Merge. After this, the mainnet Merge is expected to occur sometime at the end of September.
The network transitioned to proof-of-stake (PoS) when the Terminal Total Difficulty (TTD) exceeded 10,790,000. That occurred around 1:45 UTC.
On July 27, Ethereum announced the Bellatrix upgrade to Goerli’s beacon chain, Prater, in preparation for the testnet merge. After the Bellatrix beacon chain was activated on August 4, all that was left was for it to merge with Goerli, so it the testnet could continue to run on the PoS chain.
The testnet merge takes the project one step closer to Ethereum's mainnet upgrade later this year. The two previous testnet merges, Ropsten and Sepolia, were largely successful as well, heightening Ethereum community confidence that the actual Merge should be able to happen this year.