The large transaction
According to the transaction page on Etherscan, it was made on Nov. 11, 02:56 p.m. UTC, when Ethereum was trading around $4,810.
The transaction itself is nothing unusual since the Ethereum Foundation is constantly selling its crypto funds to receive fiat currencies, which supports the organization's activity. But the main concern of the majority of users is the timing that the foundation has chosen.
According to the market history of Ethereum and on-chain data, the foundation tends to sell its holdings 3-5% close to the next local top. The amount sold by the foundation does not even reach 0.1% of the daily trading volume of Ethereum; hence, it cannot affect the price directly.
About the foundation
The Ethereum Foundation is an organization dedicated to the support of the Ethereum ecosystem, which includes updating, sustaining and constantly developing the network.
The company claims that it exists only to support the ecosystem—not to lead or control it. Additionally, the organization claims that it does not hold a monopoly on the development of the network.