Hardware is pretty freaking hard. Just look at recent examples of public hardware companies: FitBit / GoPro. Both doing like crap, struggling to maintain their grab on the market and looking for acquirers.
Honestly, I think this is a very unattractive sector, at least in this side of the world. Most serious hardware contenders are and will keep coming from China (DJI, Xiaomi, Yi, etc).
Disclaimer: I work for Fitbit but speak only for myself.
Hardware startups have been bought before. This isn't a unique event.
I worked for a hardware startup for a couple of years and VCs being cautious about the category is very well deserved.
It is easily an order of magnitude harder to develop a successful hardware product than a success software product. And even after you've sold a million of them a design defect could show itself that makes all million of them break and destroys your entire company overnight.
It's doable but very hard.
https://www.crunchbase.com/organization/ring#section-locked-...
Looking at that it looks like at least $200 million in funding was raised. The kinds of exits for software companies that have raised over $200 million generally look very different.