ARR is not a moat at all, because the revenue of OpenAI is not preventing Alibaba, z.ai and so on from generating revenue as well. The opposite is true, actually, because the first mover prepared the market (e.g. user education about application possibilities, creating the willingness to pay for the service in the first place) for the second movers.
People here write about switching from Claude to Codex mid-workday - that is the absolute opposite of a moat.
The only companies that have a chance of not losing everything in this market are those with established non-AI revenue streams, like Google or Alibaba, or those focusing on profitability in niche markets instead of participating in the SOTA death race.