I don't think they're necessarily choosing defense. They just don't have anyone on offense worthy of being paid. Everyone on the offense is cheap because they're either on a rookie contract, they suck, or both.Not so much how they run the offense as much as how they tool it. They have chosen to invest the most money in the defense. Chris Boswell makes more than most, if not all, of the skill guys on offense. The defense is stacked with seasoned veterans.
They've whiffed a ton on that side of the ball. What are the possible explanations for having only 1 dude who would get truly paid on the open market. Bad luck? Dumb coaching that doesn't understand the modern game? Poor personnel selection? Bad development practices? All of the above? We have to be honest with ourselves that the offense has been a horror show since well prior to #8 getting the keys. Who is to blame for that?
The longer and more deeply that I think about this, the more I conclude that Tomlin just doesn't know what he's doing on offense. This leads to poor hiring, poor deployment, and poor development and ultimately 11 guys who are more or less league average players (or worse). Fans blame the players because they don't understand the game well. They just don't watch the Dolphins for 49ers film enough to see that the Steelers are playing a much different, and worse, version of the game. Or they are locked into Tomlin's glory days from 15 years ago.
I'm also not totally convinced that Tomlins is smart on defense, either, but he has 3 superstar veterans there holding the fort who could be papering over issues in a pretty significant way.