I used to work for Walmart.com (the website/app, not in stores themselves). We would cancel preorders if they were oversold without an excuse. What they're experiencing is coincidence, and it's not related to asking support questions or anything. It's literally in the support pages this will happen. Now for why Walmart doesn't inform you it's sold out prior is because they were expecting more units and were told they would arrive on so-and-so date. The manufacturer eventually says they can't fulfill all of those requests, and so Walmart.com has to cancel ones that aren't able to be fulfilled in a timely manner.
That being said, if there was an alternative to the Switch 2, like TVs have (different manufacturer or different model), and especially around the Christmas buying season, Walmart.com would typically offer the equivalent model, plus give a generous gift card (at least $100). There was a year that we even gave free TVs plus gift cards worth $300 because the orders couldn't be fulfilled as TCL has a last minute recall before these were to be sent out for Black Friday deals. But, there is no alternative to the Switch 2, and so nobody gets an offer, just a cancellation.