This story is so common that I wish there was an established economic term for it. Something like "reputational arbitrage" or perhaps "sentiment stickiness".

The basic idea is that a business can change its quality much faster than its reputation changes. If the business rapidly cuts costs and quality, their sales will reflect their reputed quality more than their actual quality for some amount of time. That gives them a window of very high profits where they can basically sell shit like it's gold.

Eventually the reputation catches up with them, but it seems to take a very long time to do so, if ever, so it's an extremely tempting business model.

There is a related but different effect where a brand establishes some level of cachet or meaningful emotional attachment back when the product was good. The product tanks, but people keep buying it even while knowing it's garbage just because of the emotional associations they have with the historical product.

The line between these two effects can be blurry. I think Pyrex leans more towards the former where people keep buying it simply because they don't realize it kind of sucks. But Jeep is the latter where it seems like everyone knows they'll spend half the time in the shop but people just like Jeeps anyway.