Complex sentence: Following his announcement, several media reports and bookmakers had speculated as to who would replace Capaldi as the Thirteenth Doctor; the bookmakers' favourites were Ben Whishaw, Phoebe Waller-Bridge, Kris Marshall, and Tilda Swinton.
Split into simpler sentences: Following his announcement, several media reports and bookmakers had speculated as to who would replace Capaldi as the Thirteenth Doctor. Bookmarkers' favourites included Ben Whishaw, Phoebe Waller-Bridge, Kris Marshall, and Tilda Swinton.