I don't know -- I feel like the SEC's point is that at the time of the tweet, nothing had in fact been secured
That's not the legal standard though: he only had to be very certain that funding is secured and tweet truthfully, without an intent to deceive - and apparently he was truthful, because the Saudis told him that they wanted to take Tesla private and already invested 5% into Tesla.
But there's more: according to news reports there was a
second source of funding as well: by August 22 Elon, Silver Lake and Goldman Sachs gave the board a formal proposal with 30 billion dollars of funding, according to the WSJ:
(Note that another newspaper only reported "German carmaker", so it's not certain whether it's Volkswagen or one of the others.)
So Elon had two independent sources of funding to take Tesla private: the Saudis, who made an offer on July 31th, and the consortium Silver Lake and Goldman Sachs organized by August 22.
So Elon was fully right if he thought that funding was secured. The big deal was shareholder approval: which indeed caused the going-private transaction to be dropped.
The SEC's legal burden is steep: they'd have to prove intent to deceive. Which would be doubly difficult because what Elon tweeted was
true: by August 22 he had
two, independent sources of funding.
So I don't see how the SEC has a case here.