Why the air pressure on Venus is so high?

The temperature of Venus is 462 degree C, less than three times of the earth’s temperature, in Kelvin. The radius of Venus is slightly smaller than the earth’s. But the atmosphere pressure is ninety times higher. How is it possible?

The state equation of ideal gas is PV = nRT. Ignoring the constant R, the equation can be rewritten as P = (n/V)T. n/V, the density of the gas, might be similar on Venus and the earth, for the gravitational forces are similar on Venus and the earth. When T is three times higher, we might estimate P is roughly three times higher.  

What is wrong with my reasoning? I could not understand why the atmosphere pressure is so high on Venus. 

Reference for relevant data

https://scitechdaily.com/from-temperate-world-to-acidic-hothouse-how-massive-volcanism-may-have-altered-venus-climate/