Broadcast stations have "Designated Market Areas" (DMA). If you are outside of a station's DMA, a competing station can force Comcast or similar to drop the outside station. Most likely, that is what happened.
Your local affiliate station owner paid big bucks to buy you as a customer. An affiliate has exclusive rights to air programming in its designated market.
For years, most affiliates didnt really care all that much, but in the past decade, many folks have *lost* their out-of-market signals. Designated markets were created in the middle of the last century and are woefully out of date in many areas, depending on how the population has grown. The FCC controls market segments. Comcast has to follow the direction given or be out of compliance and subject to fines/penalties. There are a few areas where a local affiliate may not care that they co-exiist on the same cable system, but those are far and few between.
In my area, the CBS and NBC affiliates insisted that Comcast remove the CBS and NBC stations which were roughly 90 miles aways and had been carried on local cable systems since cable was invented. They *own* the territory and want to sell ad time based on the population. If 25% of the population was watching the same program on the distant station, then advertisers wouldn't pay full $$$$. So the local stations petitioned to have the distant stations removed. And they were removed abut 5 years ago.
Luckily we still get both ABC and PBS stations. One set of channels is 75 miles away, the other is 90 miles away. Comcast proved to the *local* channels that the *distant* channels had substantial viewing and refused the request. The 75-mile-away ABC station petitions every year to have the 90-mile-away ABC banished. They fail every time. Sinclair just bought the 75-mile-away ABC station, so deep-pocket legal action will probably come next.