I know that it seems very obvious that the amount of energy required to vaporize a certain quantity of water at solme temp. Tsat1 must be less than the amount of energy to do the same thing at Tsat2 if T1>T2. And an explanation for this could be that the molecules are moving so much faster at T1 so they need less energy to escape the pressure. So the latent heat is less at T1. But what I don't understand is, if Tsat 1 = 100C, the pressure was say the atm pressure and at Tsat2=300C the pressure was 8.5 times the atm pressure, doesnt that kind of produce the same effect? What I mean is, even though the sat temp increased(and also the kinetic energy of molecules), the pressure increased as well, so it should take roughly the same amount of energy to make the molecules escape the new pressure with their higher kinetic energy. 
Why does the latent heat of vaporization decrease then?

[![This is the relation between Tsat and Latent heat of vaporization which I don't understand.](https://i.stack.imgur.com/ey4FI.jpg)](https://i.stack.imgur.com/ey4FI.jpg)