Sign of softening its positions do not mean that Israel has been changing its fundamental threat assessment regarding Iran. On the contrary, Iran still holds the main source of risks against Israel no matter what a deal might be emerged in Vienna or not. However, Israel seems preparing itself for the future in which a deal might achieved.
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Israel will make it sure that Iran will make necessary concessions which are not issue for Iran since they are also aware that they need it before public to soften Israeli security concerns. The deal might be a limited agreement or not, it is likely that it might take place this year. It will open Iran to financial institutions and would probably bring a peaceful period to region. It is vital for US imperatives since major military resources are shifted to counter rising China threat in Asia. Moreover, it will make sure that Russia and China will have limited influence in the region especially after US left.
The talks take time more than anticipated since the non-nuclear issues are also on the table. Naturally Iran wants to increase its exports by selling more oil & gas since it needs revenue for investments. Iran can easily achieve $20 billion in the initial year once deal is signed. It will boost the economic activities as well as international investments. Since Iran exposes such opportunities, US naturally wants to guarantee the maximum return by assuring that Iran will prioritize US made equipment and services purchases. Therefore, it is not only nuclear deal agreement but also shares of Iran revenue via international investments.
However the peaceful period between Iran and Israel can only last as long as the deadline on the agreement. US will not resume to region for a long time. Aftter the deadline, Iran will be free to develop high technology military equipment which might involve nuclear weapons. Without US support, Israel will be compelled to seek new allies globally. It will not be surprising to see Israel developing deeper relations with China and Russia to encounter diminishing ties with US in future.