Why is the Columbia Class much heavier than Ohio?

**Edit: I can't seem to change this post to 'answered' Getting more criticisms of the date of the image than actual details, I'd like to close this thread now. I'm satisfied with the answers I got.**

I'm very curious about the Columbia Class and would like to know how it compares to the Ohio as a nuclear missile sub. I am not presuming to know better and realize much of what we know of Columbia remains classified, so there will be a lot of speculation which I'm open to considering.

I assume most are familiar with the specs of Ohio's successor, and that the new design went with 16 missile silos instead of 24 due to advances in missile design + treaty limits. They even went from four torpedo tubes to two, as these are strictly for self defense. That being said it would stand to reason Columbia shouldn't be heavier with a smaller arsenal, and yet it's projected to weigh in at 21k tons submerged vs. Ohio's \~19k. Which means not only does the saved weight of 8 fewer silos go to something else, but another 2k tons have been added beyond that.

I'm asking because submarines are by design supposed to be as small as you can possibly build them to achieve their mission. Weight and volume are at a premium when it comes to submarine design, hence why they are amongst the least comfortable naval vessels to live and work on. Making them wider and heavier adds cost and reduces their maximum depth, so it's reasonable to assume that the specs were set to include added mission capacity. It's also reasonable to assume they sought to increase the boat's habitable space for crew comfort and provisions. And yet at the same time they elected to maintain the crew size at 155 instead of trying to automate more of the work. A smaller boat would demand fewer crew, reducing operational costs.

After looking at the above diagram I noticed they've included tomahawk cruise missiles behind the sonar, giving the sub the ability to participate in conventional warfare. This seemingly goes against its primary mission, which is to remain hidden unless/until the order comes to launch its missiles. If however the Navy brass believed it was worth adding these, I wonder why they'd put them in front rather than simply design in two or four more silos specifically for cruise missiles.

Edit: Here's a more recent depiction, since the above is considered ancient. I'll update when I'm not busy, this things resolution is terrible.