Its About Resources.
Mars has all you need. No where else within easy reach does. It's really that simple.
There are no resources but energy in Earth orbit.
There are few resources in Venus' atmosphere. It's surface is about as habitable as Jupiter's so it's pretty ridiculous to even offer it as a near term option.
The only abundant resources on the Moon are O2 and solar energy (in very limited places)
Asteroids are the best option aside from Mars in many ways, but suffer all your slings against Mars to a much greater degree.
It should take about 10% of the engineering sense common in engineers to get this obvious point imo.
see ya.