There are areas in the country where gas is all priced the same. From personal experience, it seems to be common in Idaho. Shell, Chevron, Sinclair, Maverick, doesn't matter, they're all the same price. Why? I couldn't tell you. This was the same even before covid and the current crisis.
In my area in Texas, there was always some variability. Costco was the cheapest, but then the other stations, Shell, Exxon, Chevron were all within a dime of each other. This week I have noticed the Chevron, Shell, and Exxon all the same price, which has never happened before. I think there's some psychology at play. With gas prices going up extremely quickly, people will go out of their way to make sure they're getting the cheapest price so all the stations are actually trying to compete now, instead of Chevron always being the most expensive.