Within minutes of his resignation announcement, however, Mr. Lee’s profile had been removed.

Among the areas where Mr. Sherwood and Mr. Lee clashed was programming strategy. Mr. Sherwood, whose background is in television news, saw himself as having smart opinions on scripts and casting. Mr. Lee disagreed, something that came to a head in recent weeks, as the network moved deeper into planning for next season. Mr. Sherwood had long wanted ABC to focus more on CBS-style procedural series like “NCIS,” while Mr. Lee continued to back serialized dramas like “American Crime.”

“I’m especially proud of the incredible team I built and the strategic, creative vision we established and successfully executed,” Mr. Lee said in a statement.

Not all of Mr. Lee’s programming choices paid off. “The Muppets,” introduced in the fall to significant marketing hype, has been a flop. On Tuesday night, the show fell to a woeful 0.8 rating among adults 18 to 49 — a demographic that advertisers pay a premium to reach — and had just 2.4 million total viewers, a low for the series. ABC was also the first network forced to cancel a new series this season when its drama “Wicked City” went off the air.

Among the big four broadcast networks, ABC ranks third among total viewers and last among adults ages 18 to 49 for the season that started in September, according to Nielsen data.

Of the four networks, ABC has sustained the biggest declines this season in both categories, though every competitor receives a substantial ratings boost from sports.

Image Paul Lee led an industry push toward more diverse casting. Credit... Tommaso Boddi/Getty Images

With Mr. Lee’s resignation, Mr. Sherwood, who has faced setbacks in his early tenure, including a ratings drop at ABC News and a failed effort with the cable network Fusion, will notably gain direct control of ABC Studios. As ABC and other networks face an uncertain business future, the television studio could become a growth engine, especially if it begins selling more shows to streaming services.