I have always wondered this about my job before. Lately, I've started thinking of it in this context. TLDR; I don't know this yet. Maybe there is none.

See other functions could probably build a MOAT by doing these -

For Developers - they have their OS contributions, building applications, tests to showcase their technical prowess. For Designers - they can show their portfolios, case-studies, UIs. For Marketers - camapaigns to show, numbers that were impacted. For Sales/Business teams - Their network.

Maybe then as I am looking from this lens, you could argue for a product manager the MOAT will be on the products they've launched and numbers that are impacted. But that is not holistic. Bad product managers can launch decent products and show numbers - depends on the teams that are around them too.

Is then a good product manager that critical to launching a good product?

Haha, no.

Does having a good product manager, help you launch a successful product?

I'd say more often than not.

Maybe then the MOAT can be the number of bad products I launched and what I took from that, to ensure that does not happen again.