Stoping the proliferation of nuclear weapons is of strategic interest to all countries with active nuclear weapons programs irrespective of whether or not Iran was a threat in the 60s or if Israel had a specific target for it's nukes.

I'm not saying Israel doesn't have the ability to build nukes, of course they do, as does Iran.  I'm saying they voluntarily stopped and took a deal from the US to not continue in exchange for a secret defense agreement.... but they didn't shut down the program, they just froze it, so they could continue if that deal somehow ever fell apart and as leverage to force the US to keep defending them.

But it's just a hypothesis.  Everybody in all political camps seems to think Israel has nuclear weapons, so it is a minority hypothesis.  This last week's intelligence leak gave it a bit more credibility though which is why I mention it now.