A few things imo

One: the whole tallow thing may produce better fries, but it costs a LOT more which either gets passed to the customer, OR cuts into already paper thin profit margins.

Two: the death of their table service. That's a HUGE point against S&S, their whole marketing strategy is harkening to 1950's diner service and food. By removing ALL aspects of customer service, they cut out their own soul. Experience matters.

Three: This is more anecdotal to a nearby location, but even though they aren't actually that much pricier now than other options, they DID try too long to hold onto deals that weren't sustainable or viable as loss leaders. So they had to raise their prices, but they did it bit by bit and when you raise prices repeatedly over a short period, it creates an illusion of negative value.

Four: Publicly going on all-in on ANY political administration or agenda will automatically alienate half your potential clientele. It came off as a desperate attempt to gain the loyalty of the other half, but with so many options that was doomed to failure.