There's a halo effect here. If Atlassian can drive powerful integrations with its current products then it can increase the value proposition for those products among Trello customers, driving sales for its own products. Not that there was anything to prevent them from making those integrations before, but now they can go to Trello customers directly and ask them, "hey did you know you can create a Confluence meeting notes document, create a bunch of action items during the meeting, turn them all into Trello cards with the click of a button, and see the real time status of all of them straight from the Confluence document?"
