After the Ukrainian leader's heated exchange on Friday with President Trump at the White House, Zelensky drove off in his motorcade shortly after being asked to leave. The resources deal, one of Zelensky's reasons for heading to Washington, was left unsigned.
Zelenskyy is operating without ego. He needs to keep all options open as situations and minds can change. This also has the benefit of making Ukraine look to be the agreeable party between the two for right now.