What you have to ask is: why has the Saudi King, close to his death bed, chosen a very anti-Iran man who has cost the nation of Saudi Arabia billions of dollars a month in the genocidal folly of Yemen? Did Trump have something to do with this surprise decision?
But there is a renewed decline in oil prices. Analysts have also pointed to the sharp drop in foreign reserves – $36bn in the first four months of this year. The conflict in Yemen has killed thousands of civilians, created a famine and is going nowhere, while reportedly draining Riyadh’s coffers of billions of dollars a month. The new crown prince (then defence minister) led that rush to war, baited by the country’s intense rivalry with Iran. His hawkishness has manifested itself again in his public remarks on Iran – suggesting further escalation is likely – and this month’s startling blockade of Qatar: the biggest diplomatic crisis to hit the Gulf for years. Regional jockeying for power and his closeness to Mohammed bin Zayed, the crown prince of Abu Dhabi, are key. But so too, one suspects, are impatience and inexperience.
[source : The Guardian view on Saudi Arabia’s crown prince: the age of ambition, The Guardian, https://www.theguardian.com/commentisfree/2017/jun/22/the-guardian-view-on-saudi-arabia-crown-prince-the-age-of-ambition?CMP=twt_gu, 22nd June 2017]
And those hawkish "public remarks on Iran" are these:
“We are a primary target for the Iranian regime,” Prince Mohammed said, accusing Iran of seeking to take over Islamic holy sites in Saudi Arabia. “We won’t wait for the battle to be in Saudi Arabia. Instead, we’ll work so that the battle is for them in Iran.”
[source : Dialogue With Iran Is Impossible, Saudi Arabia’s Defense Minister Says, New York Times, https://www.nytimes.com/2017/05/02/world/middleeast/saudi-arabia-iran-defense-minister.html, 2nd May 2017]