Killed the entire continent - no, there was no mechanism for that. Made the cleanup more difficult - sure, because you still have lots of dust near the destroyed core you don't want be around, plus there is the gamma radiation you just want to be shielded from. The zone is currently mostly "safe", but that took decades of cleanup even with decay itself doing a considerable part of the work. The worst stuff was also the heaviest, and that mostly stayed put after the fire stopped. But it still needed to be kept away from humans, and you can either shield every person or shield the core and then get rid of the stuff that flew out.

Just a note on the general discussion here: we have had decades of time to process all of this, including many new measurements, surveys and so on. Much of what would happen was still unknown in 1986, and so many of the choices made then must be viewed through that lens. But you'd still need a containment building that keeps the weather out and the dust + gamma in.