Basically, this means that key elements of a show is drastically changed based upon the demands of the executives (https://tvtropes.org/pmwiki/pmwiki.php/ExecutiveMeddling/LiveActionTV) running the network for which the show airs on. This is usually done in hopes of making the show more appealing to audiences.

Too much meddling?: Phyllis (format, cast), Doris Day (format, cast), Valerie (cast), Wonder Woman (period/format/tone), Mom (format/cast), The Judy Garland Show (format), The Lucy Show (format/cast), Batman (tone/format), I Dream of Jeannie (marriage), Rhoda (format/marriage), Lost in Space (tone), My Three Sons (cast/tone)

The Cast Purge on the Facts of Life was one of the dumbest things I've seen. "Too many girls" at a girls' school is ridiculous.

The meddling on Fox's Firefly was also crazy. They aired sequential episodes out of order! WTF?!

The Lucy Show changes were horrible.