A product gets good reviews in Consumer Reports or the Wire Cutter or reddit, and the company making it knows they're gonna sell a ton of them, so they start cutting corners, or even start selling a slightly different product with the same model number.
Or you find a decent brand that makes good products, they get popular and grow and in come the MBAs with ideas on how to increase profits. Or they get bought by Private Equity and carry on only by brand momentum.