I believe this was a marketing ploy on their end. They likely only ordered a very (very) limited run so that they can say demand was so high they sold out.
Bethenny has 1.8M IG followers and 1.6 Twitter followers (and there's probably some overlap). They hyped up this launch for months to millions of people, which means they should have anticipated a high demand, especially if they were partnering (if even for a short time) with a well known retailer that not only has brick & mortar stores, but an online presence as well. Instead, it seems to me that they cared more about the hype than the delivery.
It's a similar thing that Kim Kardashian West (KKW) did last summer with her makeup launch. Kim has 118M IG followers and exactly half the number of followers on Twitter (59M), which means she has a captive audience. And what did she and her company do? Have only 300,000 kits for sale, which sold out in hours. This way you get the press about how hot the product is, even if it means frustrating those of your fans who might have wanted to get their hands on the thing.
Contrast the games that both Bethenny and Kim played with Rihanna and her Fenty Beauty launch last fall (Rihanna has 64.9 million IG followers and 87.8 Twitter followers). As with Bethenny's product and KKW's product, the hype for Fenty Beauty was real. There was a lot of anticipation leading up to the September drop. Fenty Beauty partnered with Sephora, which, like Macy's, has brick & mortar stores as well as their online platform, and they made sure that they would have the supply to meet the demand. It seemed less important to them to boast "SOLD OUT PRODUCT!" and more important that people actually had the chance to buy the goods.
Point: If someone really wants to have supply meet the demand, they can.