To quote Oracle's 2021 definitive proxy statement, "As of September 13, 2021, Mr. Ellison, Oracle’s Founder, Chairman, CTO and largest stockholder, had pledged 317,000,000 shares of Oracle common stock as collateral to secure certain personal indebtedness". On that date, ORCL closed at US$87.91. So Larry Ellison had pledged approximately
US$27 billion of ORCL stock to cover his personal loans. That doesn't tell us how big those loans actually are, but obviously the loan principal is in the billions not millions – it could easily be over US$10 billion. So if banks are willing to lend Ellison a few billion, why not Musk too?
Also, Musk may be able to find some co-investors (fellow billionaires, private equity, etc) who believe that Twitter would do better with a Musk-selected executive leadership team than with its current one, and so would be willing to support Musk in taking control.