I'm not sure what you mean with Venusian colonization. The surface is so utterly hostile that all probes we've managed to land only last for at most a few hours due to the intense atmospheric pressure, corrosive atmosphere, and temperatures hotter than the melting point of lead.
Floating balloons were considered, but it turns out those have a whole host of practical engineering concerns that rule them out. Plus, getting back into orbit is nearly impossible from said cloudtop balloons. You'd basically need a full sized orbital rocket like the Falcon 9 because the gravity is basically the same and the atmosphere is still a major concern.
Musk is ~50. His goal is to get a colony on mars. Mars is probably a lot easier to start with. Venus is a target probably 50 years after all of us have died. Its going to be the goal of someone that has likely not even been born yet. He is serious that's why he is aiming for an achievable goal. Venus is not an achievable goal with our technology level.
If he were to come out and say "Mars is the stepping stone that I can do within my lifetime, and Venus is the real goal we can only think about once we establish the demand on Mars, probably after I'm dead", that would be great and I would have more respect for him.
Mars is easier to "practice on", and get some toy colonies going, but once scale starts to matter, Venus is better.
At some point, you rather have too much energy and good self-sufficiency at geological scales, than too little energy and bad self-sufficiency.
Of course this stuff has been debated endlessly, but I do not recall reading the "Mars is the stepping stone, Venus is the real deal" needle thread.
If Musk was serious, I think he would admit this, rather than hype-beasting the stepping stone and the real deal.