Density and Time.

Density: A meteor's energy release could be described as a long narrow cone. An atom bomb would in a dense sphere/hemisphere. To make it comparable you'd have to get the meteor to expend all it's kinetic energy in one spot (due to interaction with the atmosphere this is unlikely). The shockwaves are spread out over a larger total distance. I.E. Less concentrated.

Time: A nuclear weapon releases all it's energy in milliseconds into a single pressure wave. A meteor tends to shred itself slowly in the atmosphere (relative to a nuke). Time is immensely important when measuring the destructive force. Slowing a car from 50mph to 0mph is the same 'total energy' if you do it in 10seconds or .1 seconds, but the car will suffer significantly more in the .1 second scenario.

My impression of the Chelyabinsk meteor was that it fragmented significantly about 14-15s after first appearance. This would have greatly increased its surface area, and likely wasted a significant portion of its kinetic energy at that point. So the power delivery curve wouldn't be completely smooth or continuous.

That said, a nuclear device delivers virtually all of its energy as ionizing radiation (5%), thermal pulse (30-50%), blast (40-50%), and residual radiation (5-10%). The actual nuclear reaction takes less than 0.5 milliseconds, the thermal radiation pulse generally lasts several seconds, more for exceptionally large weapons (e.g.: Tsar Bomba, 50 MT).

The distinction between total energy delivery, and rate of delivery, is key. Gunpowder and TNT are actually significantly less energy dense than kerosene, but release that energy much more quickly. The destruction of the WTC towers in 9/11 was the result of aviation-fuel driven fires burning in a structure for many minutes, rather than a single explosive pulse.

The mode of energy delivery also matters. For a meteor, the principle delivery is heat, light, and shock. With nukes you've got both ionizing radiation and fallout to be concerned with (generally 10-20% of total energy).

This is also a point I raised regarding financial market collapses, when a professor tried to point out that the stock market had survived 25% declines before the 1987 crash. Sure, but over time. Would you prefer going from 60 MPH to zero in 4 seconds or 0.06 seconds (about the time it takes your seat front to find the front bumper in a static-barrier impact)?

Since we are talking total energy release, it becomes hard to compare them since a meteorite dumps a significant amount of it's energy into the atmosphere in a much slower and widespread fashion, whereas a nuclear device does it in one place at one time.

Now I'm pretty sure that if you get a big enough meteorite moving fast enough, the distinction becomes much fuzzier and the real important factor becomes just how much thermal energy was added to the atmosphere.

A lot depends on the angle too.

I believe it is because most of the damage done by a nuclear bomb is caused by radiation, not by the initial blast (do correct me if I'm wrong, I am by no means an expert).

Not really. The fallout can be a significant danger, depending on the bomb size and design. However, it's much easier to survive than the initial blast, in general. It can be a substantial problem for survivors, but the blast will kill far more.

The main reason the explosions aren't comparable is because this meteor exploded far higher than a nuclear bomb would detonate. By the time the blast reached the ground, the energy had been spread out over a large area. If it had exploded at a typical nuclear bomb detonation height (say, 1km or so), the destruction would have been comparable, although survivors wouldn't have to worry about finding shelter from fallout.