I've heard that Thoma Bravo specializes on re-selling assets. If that's true then the $15bln sticker on Tableau should only justify and boost their intention to re-sell Qlik.
Haven't heard much about Qlik lately. A few years ago we were evaluating Birst and Qlik, and have since settled on Looker and Tableau.
Birst end up getting acquired too. https://www.infor.com/news/infor-to-acquire-birst-infor
Not sure if that's a relative bargain compared to this deal or if it makes the $15.7B look totally unrealistic. As of a few years ago the total revenue of the two firms wasn't that different.