First: The Shiite Iran has been scoring victorious points in context of the eternal stand-off with the Sunni Arab states and communities in the region while overcoming the political isolation of the last decade (Tehran invited to take part in the Vienna format pertaining to the Syrian crisis) as well as economic isolation (Iranian oil sales accounts in Europe have been unfrozen recently);
Second: doing that, the West seems to have been turning a blind eye on the Iranian interference into the domestic affairs of the Arab countries while instigating the Shia communities to confront and even to overthrow the Sunni rulers in their respective countries;
Third: Russian intervention in Syria ensured the Bashar al-Assad survival as well as a partial success of his troops in some swatches of the frontline which implies the growing radicalization within the opposition ranks (the more radicalized the groups are the more attractive are they for the moderates in search of their survival in the face of the Assad's troops and Shiite Hizballa advances):
Forth: all mentioned prevents Saudis and the US to form the moderate participants side for the next negotiations tour planned for the end of January;
Fifth: the increasing efforts on the Russia and Iran's side to blame the Saudies and the other Gulf monarchies in propping up the Radicals and terrorists in Syria (ISIS)
To reverse the course of events, Er-Ryadh took the approach known as "blowing up the situation" - in this case by carrying out the death verdict of the Shia preacher Nimr al-Nimr. It entailed the mass protest in Iran leading to the destruction of the Saudi diplomatic buildings - namely, to the clear violation of the international law by the Iranians. To note that the Saudies avoided any violation of the international law while reminding to the West that Iran doesn't fulfill all of its commitments assumed and does keep on meddling into the domestic affairs of the Arab States by instigating the Shia communities there to rise up against the Sunni rulers.
The Saudi act might be regarded as a message to the West to slow down reproachment with Iran once the latter refuses to fully complete its commitments. Otherwise, it is implied, such a haste might cause the new tensions in the region.
As result the Saudies seem to have succeeded in shifting the focus from the stagnating conflicts in Syria and Yemen to the always hot Sunni-Shea stand-off to mobilize its backers among the Arab and Muslim countries against Iran. It looks achievable due to the enhanced polarization between Sunni and Shia through the artificially widened gap between the two poles.The detailed analysis are here: TV channel "The Rain"
And on the site of the "Echo of Moscow" broadcast