What prevented Israel, c''v from being swept by a nuclear strike in 1968?

According to the official bulletin of the Russian Presidential Archive “Rodina” (“Homeland”, 1996, issues #7-8), a nuclear strike (from amissile carrier submarine K-172 – “Echo-2 class” - about 400-feet long) against Israel was once ordered by the Soviet Politburo. The “At least eight new Hiroshimas” as proudly put it the magazine, were going to take place in Israel, just before celebrating the first day of Pesach 1968. If happened, the tragedies would have been much more devastating than in Hiroshima, since each warhead was 1 megaton - about 50 times more powerful than in 1945. The attack was plotted the next year after defeat of the Islamo-Nazi coalition in the 6-day war, which Soviet communist leadership took personally. The pretext of the assault was supposed to be US-Israel landing on the Syrian shore (very “plausible” - Israel starts the attack in Pesach). BTW, remember Arabs started their next attack in 1973 at Yom Kippur.

The story was corroborated by rear-admiral Shashkov (in 1968 the kamikaze mission submarine commander, and two former Soviet Navy chiefs Chernavin and Gorshkov. For weeks, the submarine had to pop up every 2 hours in order to get last minute radio confirmation to the 8 missiles launch – but he never got that confirmation. The article author believes that the Czechoslovakia events change the Soviet Politburo priorities at the time. “Czechs saved Israel for the second time" – first time was 1947, when Israeli received weapons from the Czech arsenals.