While both Epsilon and Acxiom were in the data marketing world, they offered different solutions. IPG bought Acxiom in 2018 for $2.3 billion, and Publicis bought Epsilon in 2019 for almost $4 billion.A second source directly familiar with both data units noted a stark difference in how each holdco integrated them.Sadoun demanded all of Publicis work with Epsilon.“It was top-down,” this source said. “The leadership and tone from the top made all the difference. It was very much, ‘This is the way it’s gonna be, and if you don’t like…