She used to manage 3 employees. Now she oversees 24. Welcome to the age of the megamanager.

Match group's Chine Mmegwa oversees a much bigger team than she did a year ago, a change that's become common for middle managers across Corporate America.

Lucía Vázquez for BI

On a recent weekday afternoon, Match Group manager Chine Mmegwa sat at her desk in a New York office, looking up at her team through a mounted TV screen.

The meeting was much like others she'd led during her first few years at the dating-app company, only with a lot more faces. That's because she now oversees two-dozen employees...