There seems to be little doubt, according to Baer,  that these
assassinations have been an Israeli operation, but the weakening effect on
Iran’s nuclear program is far less significant than the fact that this could
easily provoke Iranian retaliation and achieve the desired US/Iranian war.
(I would add that if Iran refuses to respond in a belligerent fashion, there
is also the possibility of an Israeli false flag attack against US citizens
which could be blamed on Iran.)

Matthews should be given credit for allowing mention of  the effort of
Israel to manipulate the US into a Middle East war, which is a mainstream
taboo. Of course, Israel has been pushing for war with Iran for over a
decade; and the Israel lobby in the US has been making the effort to have US
Middle East policy coincide with Israeli interests.

The neocon Middle East  war agenda certainly included regime change in Iran,
though it sought much more.  Saddam Hussein’s Iraq, being perceived as the
weak link, would be the first step for the elimination of  all regimes
hostile to Israel in the region.  The neocons sought to make Iran the Bush
administration’s second major target and were successful in creating a more
hostile US policy toward  that country,  but they were unsuccessful in
bringing about war due to resistance from influential  establishment
non-neocons within and outside the Bush II administration  and the
diminishing desire of the American people for war, which had been white  hot
after the  terror attacks of 9/11.  I go over this history in my book “The
Transparent Cabal: The Neoconservative Agenda, War in the Middle East, and
the National Interest of Israel.”   
http://home.comcast.net/~transparentcabal/