You are kidding, am sure.
Not everyone doing it for delegations. When I started, didn't even know about the delegation. And even after learning, not really hoping for it, because lefts face it, hundreds doing the challenge, 77k SP divide by those hundreds, would not be SO big in the end.
And have you seen the people who participated? @theycallmedan, @andrarchy, @lindseybowes, these people are power player of Steem with massive SP, just to name a few. They certainly dont care for delegation but to promote Steem, dapps, and health.
Most doing it just for the sake of promoting Steem.