Yemeni drones are no longer coming for Saudi refineries. That may take some looking into.
I think the Saudis looked at the cost/benefit and realized the war was about to spiral into something much worse and decided to cut their losses:
During the Munich Security Conference in February 2020, Saudi Arabia’s foreign minister, Prince Faisal bin Farhan, signaled that the Saudi-Houthi backchannel talks were not “ready to move to the highest level.” However, the situation changed following the Houthi ballistic missile attack on Jazan and Riyadh in late March, and on April 8, the coalition’s Joint Forces Command announced a two-week unilateral cease-fire in Yemen. This came just a week after the Saudi ambassador to the country, Mohammed al-Jaber, invited the Houthi rebels and the Yemeni government for talks in Riyadh.