Why can alkoxides leave in the E1cb mechanism? Why can alkoxides leave in the $\text{E}_{\text{1cb}}$ mechanism? I refer to the mechanism below. I would think that the anion formed from the first step would be more stable than the alkoxide ion, because the charge on the alkoxide ion is intensified by the electron-donating alkyl group, making it less stable. Correct me if I am wrong. 



image source: https://en.wikipedia.org/wiki/E1cB-elimination_reaction
The fact that the elimination of $\ce{EtO-}$ leads to the generation of a carbonyl bond makes this a feasible reaction. Also, the $\ce{EtO-}$ ion generated can then take $\ce{H+}$ from water taking the equilibrium further in the direction of the forward reaction ( the net constant would be ~ $10^2$).