Activist investor Nelson Peltz is fighting for a seat on the board of Walt Disney Co., claiming that the theme park and media company is struggling with self-inflicted problems.

Bob Iger, the enterprising entertainment executive who brought Star Wars, Pixar and Marvel under the Disney marquee and challenged the streaming dominance of Netflix, will replace his handpicked successor, CEO Bob Chapek, whose two-year tenure has been marked by clashes, missteps and a weakening financial performance.