Short answers, pulled from the story.
Albert Einstein published the paper titled Cosmological considerations in the General Theory of Relativity in 1917. He added a specific term to his field equations that he called the cosmological constant to force gravity into a static universe model.
Edwin Hubble confirmed through observation by 1929 that the universe is expanding. This discovery led Einstein to abandon the cosmological constant and accept a dynamic universe.
Saul Perlmutter, Brian Schmidt, and Adam Riess jointly received the Nobel Prize in Physics in 2011 for this work. Saul Perlmutter worked at Lawrence Berkeley National Laboratory while Brian Schmidt led efforts at the Australian National University and Adam Riess operated out of the Space Telescope Science Institute.
The discrepancy between theorized vacuum energy and observed values exceeds some 120 orders of magnitude. This gap has been called the worst theoretical prediction in the history of physics.
Current measurements indicate around 68% of the universe's mass-energy density comes from dark energy. Data from the Planck Collaboration published in 2018 estimated the dark energy density parameter at 0.714.