[necubi]

It's really not a huge red flag. Co-founder breakups are incredibly common. In this case the company is also flailing and has been likely written off by their investors, so they're not going to care.

Something I've learned doing a startup and talking to a lot of other startup founders is that one of the biggest risks is sticking around for too long just because there's still money in the bank. Your most precious resource is time, and if it's pivot-hell for 18 months you're well into sunk-cost land.

[willseth]

If he wants to found another company he will need to pitch to investors and will be thoroughly interrogated about his experience before they will consider giving him money, and it’s a lot harder to sell a backstory where you bailed on your last startup.

[notahacker]

A backstory where he explains dispassionately that after repeatedly unsuccessfully pivoting into industries neither of them understood, he came to the conclusion his cofounder wasn't learning from these mistakes and he needed to take a different approach even if it meant starting again with nothing doesn't sound any harder to sell than a backstory where he explains the rationale behind pursuing four more pivots he didn't believe in before running out of money. Also sounds like a situation where his existing investors have probably written off the money and may even agree with his perspective on the pivots.

Bailing from a startup with significant traction or bailing when it's too early to tell could be much harder to explain away, but it doesn't sound like that's the problem here...