That depends a whole lot on a lot of details not presented, I believe.

For instance - did the founder have an explicit plan to do this in advance? Did they materially misrepresent their intentions to the investor while having this plan, with the intent to receive funds they otherwise would not? Was the investor concretely harmed by this misrepresentation?

For instance if the investor still profited, it would be very difficult to argue fraud - not impossible of course. If the founder was thinking of this plan, but never wrote it down or said it to anyone, good luck proving fraud. If the founder had never been explicit to the investor, or was never asked by the investor what their plan was, so never materially misrepresented anything (even if the investor was clearly assuming), that would also be hard to argue fraud.

Especially so if the investor had a decent amount of wealth or experience.

This is why transparency - and due diligence - are so important for all parties. And why it’s important to not put all your eggs (or even most of them) in one basket. For everyone.