Question about 2010 Flash Crash

From wikipedia:

In April 2015, Navinder Singh Sarao, a London-based point-and-click
trader,[63] was arrested for his alleged role in the flash crash.
According to criminal charges brought by the United States Department
of Justice, Sarao allegedly used an automated program to generate
large sell orders, pushing down prices, which he then cancelled to buy
at the lower market prices. The Commodity Futures Trading Commission
filed civil charges against Sarao.

My question is: how can simply generating sell orders push down the price? For the "price" to move down, the sells have to actually get executed, to reflect the last traded price.