Saudi-Iran relations have always been sour. Other than a short period of friendship during King Faisal, who was assassinated, our relations have always been bad.
And most of your claims are false. Saudis created propaganda videos of invading Tehran in 2018. They have killed hundreds or maybe even thousands of Iranian pilgrims twice, on two different occasions during Hajj. MBS publicly said in several interviews that he was going to bring war into Iran. Saudis have constantly backed territorial claims of the UAE against Iran, have openly called Iran an occupier of the three islands, and provided military and financial support to Iraq during the Iraq-Iran war. They supported Saddam's claim on the Khuzestan province of Iran as well. They have been telling the US presidents to cut "the head of the snake" since at least 2011.
Out of all Arab countries, they are by far the most hated Arab country in Iran. And this is a sentiment that is shared by the majority of Iranians.