Why do the big corps succeed (Google, Apple, Amazon) and the startups fail. I guess all three of those have had failed hardware products and successful one as well. So they can afford a failure? Startups just need more runway?
The big ones all caught a wave and rode it, while these startups tried to create the wave. (Actually, that's not quite true - all these hardware startups were riding the wave of cheap Chinese components and free trade. It's just that it turned out the bottleneck for a hardware startup isn't manufacturing, it's customer acceptance. Apple rode the same wave with the iPhone/iPad, but they also had a well-established core competency of knowing exactly what the customer wants.)
There are still waves going on now, and there are probably some startups being founded right now that will get rich off of them. It's just that the waves probably aren't what VCs think they are.
Amazon is putting large ads on the amazon.com homepage for it's products. I don't think if a startup had build exactly the same product they would have been succesful.
Apple had Steve Jobs, who had both a great vision and a cult of personality that made people buy apple products. Apple didn't have another major successful new product since Steve passed.
Google doesn't really have that many successful hardware products, except maybe Chromecast (which benefits integrations with youtube, chrome, etc.), Pixel (which benefited from good timing, the biggest competitor had to recall their flagship phone) and Home (which has less market share than alexa and benefits from Google's NLP technogloy).
Chromecast is only successful because it's so cheap. Similar as much of Amazon Echo's success is due to the discounts they often offer. That's nothing a startup could really compete with.
Big corporations are ok with costs of creating a low margin hardware product because it is loss leader to other products and services with higher margins.
Bringing a hardware product to market costs a minimum of $7m in the US. At Seed/Series A, this is a huge amount of money for investors to swallow.