As others have mentioned, Randalls and Tom Thumb were purchased by Safeway in the early 2000's, which almost immediately stripped out many of the upscale/prepared foods which originally set the chains apart. Safeway was banking on brand reputation alone, while essentially forcing their west coast store model on Texas. Meanwhile, HEB was in the early stages of upgrading their first-gen Pantry stores to full line HEB locations, and they were able to take the crown for "local" grocer from the watered down Randalls. This all happened amazingly quickly, as Safeway went through a massive round of store closures in both Houston and DFW in 2005 (I believe 26 stores in total). Under Safeway management, Randalls was at least able to maintain an upscale-feeling shopping environment in most of their remaining stores (mostly due to Safeway's Lifestyle store program), but overall the Randalls/Tom Thumb banners were badly mismanaged.
Then, when Safeway was acquired by Albertsons in the mid 2010's, they stripped out even more store features and replaced the soft mood lighting with dollar store bare fluorescent fixtures, taking away the little brand distinction that Randalls still had. Meanwhile, HEB and Kroger have both continued their respective market buildouts, growing into newer suburbs while leaving Randalls' footprint mostly concentrated in established upscale areas of Houston where there is little open real estate for competition.
Now, up the road in DFW, the same trend is starting to take hold in DFW, with HEB quickly expanding within the market while many longtime Tom Thumb/Albertsons locations stagnate. It will be interesting to see what Albertsons' long term plans for the market are if the proposed merger with Kroger fails (which is highly likely). Tom Thumb does continue to grow and open new stores in DFW, so maybe they are doing better than expected?
