One of the early ideas about the Solar System, which still persists today, as evidenced by this post, is that the planets formed in sequence and evolved through similar stages. Much of this concept dates back the times of Lord Kelvin, who supported a brief-lived sun, gradually cooling.

In this scenario, Mars was an older Earth-like planet and evolved to a "higher state" before it began to cool too far and dry up. Here are Lowell's canals and H.G. Wells' tripods. Venus was often envisioned as a less mature world, still sweltering in the equivalent of our Carboniferous age with global swamps and permanent clouds.

We now know that this is total nonsense. All the planets formed together, and evolved together at broadly similar rates, under a gradually *brightening* Sun.

Your model is the reverse of this, but still based on the same fiction of sequential development of habitable worlds.

There is some small shred of validity in the model of Venus being almost Earth-like in its youth and rapidly changing as the sun warmed until its atmosphere experienced a catastrophic runaway greenhouse event that boiled its oceans dry and even stripped its atmosphere of hydrogen.

What is not at all probable is some fantasy of C.S. Lewis-style Cytherians evolving to a higher plane and escaping the fate of their planet. There just wasn't enough time between Venus stabilising and boiling. Even at a slightly faster rate of chemical evolution permitted at the warmer temperatures, it wouldn't be enough, IMHO.

In chemistry, reaction rates roughly double for every 10K of temperature increase. Early Venus would need to have been 20K warmer than the Earth has been over the past 4.5 Ga to acheive similar reaction extents in only 1 Ga. Whilst this is possible, note that it has the equatorial ocean of Venus steaming at 55 Centigrade - sufficient to slowly poach an egg. Of course, extremophile life is possible, but complex extremophile life has never evolved on Earth - all complex organisms live at much lower temperatures.

The problem with accelerating chemisty is that too much acceleration leads to gooey tar, rather than organic structure.

Hands up all those who've burned something while trying to cook in a hurry?