Only if their portcos don't build products people buy.

Making a pure-research, foundation model company is silly. Make a product company that sells products.

Google and Microsoft both bundled their AI offering into their office suites because they weren't getting traction as an add-on.

Startups don't have that option.

They did that because

1) Their initial AI offerings weren't real products customers would use or pay for

2) They weren't seeing sufficient adoption to justify the expense

3) They have insane levels of distribution in their existing product lines and can incrementally add AI features

This is entirely orthogonal to whether or not other startups can build AI-first products or whether they can position themselves to compete with the giants.

Yes as you point out in #1, they failed to develop an AI product and #2 they failed to get traction in the market.

What moat does an AI startup have that will prevent them from being crushed by big tech?

Same moat as any non-AI startup? What do you consider an AI startup?