And their decision wasn't based on "this statement" alone. It was based on *80 years* of waiting for the Dems to make better decisions and fulfill promises, that never happened.
They'd already given up on Biden. They were giving Harris a second chance. This statement and other actions destroyed their confidence that this time would be any different.
It's easy for us to see their act as unwise. Harder to see ignoring their needs or attempting to go after swing voters as unwise.