This has been coming for a while, but it's still sad and hard to believe. Most malls manage to last a good 30 years or so -- City Center barely made it past 10 before customers and stores started leaving.
I'd actually been over there quite a bit last year, because I was dating a girl who owned one of the few remaining businesses. The shop spaces were still very nice, and it was weird seeing the upper two floors essentially abandoned. There's certainly no good reason to tear it down, but it's hard to see what else could be done with the place. Offices or something, maybe. Ultimately, the problem is that it's hard to repurpose an indoor downtown mall, which is why storefronts and shopfronts make more sense. If you walk through the Short North, you'll see that an old car dealership has been turned into a restaurant, for example.
The funny thing is, someday the City Center will be part of Columbus' forgotten history, and people will regret that it had been torn down.