In the 1970's and 80's, Tupperware was functionally superior to widely available alternatives. If you wanted a reliable tumbler with fitted lid that didn't leak or a bin to keep celery fresh, Tupperware was the way to go. Pyrex glassware was available but the lids were leaky and/or low durability...most of them still are. And it looked good.
There really wasn't anywhere for Tupperware to pivot, and the death seems natural.
And it wasn't Earl Tupper who did the marketing. It was a woman (of course I now forget her name), who invented the Tupperware Party and was basically the face of the company for many many years. She was then fired by Tupper and basically erased from the company's history until recently. There's a good documentary on it, very interesting.
I suppose they were making a unique product, but it was the grassroots marketing that made them a standout and a household name.
I believe that those suburban home-based "parties" bridged the gap between door-to-door salesmen and catalog/online sales.
In my neighborhood, "Tupperware parties" were not stigmatized or dreaded, but just seemed like a fun way to pick up some durable modern containers.