So Einstein makes a theory about gravity being a geometrical curvature of space, theory fails miserably, so Einstein doctors it by adding a cosmoillogical constant to counter his curved space gravity, and it fails again. It first predicts that the universe contracts, then postdicts that it is static, and then when he removes the cosmoillogical constant his relativistic universe amazingly stops contracting, and starts expanding, just like Frieddman predicted. Who's Friedmann ? A russian weatherman who not only was much smarter than Einstein, but also understood Einsteins theory better than Einstein himself, who was so stupid that he made two wrong predictions and postdictions in a row. Thats why Einstein said in a moment of frustration that: 'Ever since metamaticians have invaded my theory of relativity, I myself dont understand it anymore'.
Then big bang scientists revive his cosmoillogical blunder and interpret it as dark energy of vacuum. Except acording to Einstein vacuum has no energy because it has no mass. And also according to Einstein energy does not expand space but curves and contracts space. So the energy/mass of vacuum, assuming it exists, just makes the universe contract, and not expand.