If you scroll halfway up the page, you'll see that I wrote "I don't dispute that a Gorbachev was necessary. But it would be hard, given Gorbachev's own statements, strategies, and actions, to show that a Gorbachev without a Reagan would have been sufficient."

Still, the economic disaster would have been there, and so would the military and political challenges posed by the US, and so would the military disaster in Afghanistan, and so would Chernobyl, and so would the restive satellites. Ligachev may not be Gorbachev, but he isn't Stalin-- he can't force a fundamentally broken system to function simply by terror and force of will. I don't know what happens to the USSR and its satellites in this scenario, but they're on the ropes and the other guy is pressing hard-- something has to give. (Though the results might well have been more violent, and the outcome less happy. I freely grant that Gorbachev's willingness to kill people retail, but not wholesale, to keep the empire together represents a dramatic improvement in Soviet leadership.)

As for external security, Kaplan's point is that Gorbachev was emboldened to undertake reforms precisely because he figured that Reagan wasn't going to attack the USSR.

Then why didn't he respond to our military buildup and SDI program with a shrug, massive military cutbacks, and an attempt to reroute those resources to the rest of his ailing economy? If Reagan's major contribution was to make the Soviets feel secure, they had an odd way of showing it.

Is it a big surprise that Eastern Europeans were more inspired by Reagan than by Gorbachev?

Not really. What surprises me is that anyone is more inspired by Gorbachev than by Reagan.