Trello = Atlassian, they already have a heavyweight wiki tool. Asana/Slack, why would they go outside their core competence.

But even if a company did want to copy something, it really comes down to passion and execution, I've seen this play out a number of times.

Trello, actually, makes a point here. Atlassian paid $425M for it, when they could have just copied it. There's a lot more to it.