In British ScFi in my opinion Blake’s 7 is the best example of that! They replaced Blake the lead character after the second season, the character the show was named for! They showed rolled on for two more seasons. He’s brought back for the final episode of the last season. The show is a SciFi cult classic.
Blake’s 7 started it all...
The same story line has been manipulated, copied, and expanded very successfully ever since the show expired...