1) Marwan Barghouti (Fatah leader of the uprising in the West Bank) told The New Yorker in Jan 2001: "The explosion would have happened anyway... But Sharon provided a good excuse." https://www.newyorker.com/magazine/2001/01/29/arafats-gift
2) UK Parliament Hansard (Apr 16, 2002) quotes the semi-official PA daily Al-Ayyam (Dec 6, 2000) reporting PA communications minister Imad al-Falouji: "the Palestinian authority had begun preparations for the outbreak of the current intifada... in accordance with instructions given by Chairman Arafat himself" and that it was not meant merely as a protest over Sharon's visit. https://hansard.parliament.uk/commons/2002-04-16/debates/d69... (search within the page for "Al-Ayyam" or "Al-Falouji")
3) Arafat's widow Suha said Arafat decided to launch it ("Because I am going to start an Intifada") on Dubai TV, per MEMRI translation, quoted by CFR: https://www.cfr.org/articles/arafat-and-second-intifada https://www.memri.org/tv/suha-arafat-widow-yasser-arafat-200...
Also, this is not some uniquely Israeli talking point. Britannica describes the start as Palestinians erupting into violence after Sharon's Temple Mount visit: https://www.britannica.com/place/Israel/The-second-intifada