Goldberg thinks the most common answers are less than compelling. It's unlikely, he says, that "Iranian nuclear knowledge is so concentrated in the minds of a few scientists" that these killings are a major setback to the nuclear program. And he doubts that the killings will scare much Iranian talent out of the nuclear science business, since the Iranian government wouldn't tolerate such an exodus.
But there's a third option that Goldberg doesn't consider: Israel is trying to start a war with Iran. The more Iranian scientists it kills (and the more missile testing facilities it blows up), the more likely Iran is to retaliate. And things have a way of escalating, which would pave the way for military strikes on Iran's nuclear facilities.
Obviously, Israel could bomb Iran's facilities even without such escalation. But escalation offers two advantages:
1) Israel gets less blame, because it isn't accused of starting things. Of course, from Iran's point of view, Israel did start things by assassinating Iranians and blowing up Iranian stuff. But whether assassinating foreigners is bad depends on your point of view. In the eyes of the west and especially the United States, it's terrorism when Iran does it but not when Israel or America does it.
2) The United States is more likely to get drawn into the war. Israel presumably prefers that America do the lion's share of the bombing of Iranian nuclear facilities, since the U.S. has deeper strike capabilities. If Israel launched strikes on Iran out of the blue, while the U.S. still considered a diplomatic solution to the nuclear standoff possible, Israel couldn't count on the U.S. joining in. But America would certainly spring to Israel's defense if Israel found itself in an escalating war with Iran that Iran was blamed for starting. And once America was involved in hostilities, it would probably take the opportunity to set back Iran's nuclear program.
Personally, I don't find the Israeli assassinations as perplexing as Goldberg seems to. Though bomb-building knowledge per se can't be extinguished by killing a few scientists, talent is always a scarce commodity, and removing key talent from any enterprise can set it back significantly. So I don't think Israel is assassinating scientists just to draw America into a war. But it wouldn't surprise me if, from Prime Minister Netanyahu's point of view, that prospect isn't exactly a deterrent.