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).