I think Bibi and everyone in the Mossad and the IDF were overconfident and complacent. Hamas got help from Iran and their tactics have evolved.
Not everyone:
https://www.jewishpress.com/news/israel/idf/general-brik-who-warned-about-the-hamas-invasion-the-idf-cannot-fight-on-2-fronts/2023/10/08/