I have been told that Burghardt was part of Terpstra's G2. If that is correct, and if he managed to slow the chase, even a little, that could have made all the difference. At 20km to go, Sagan-Dillier had pulled the gap out to 1:30. Between 18km and 8km Terpstra et al managed to gain back half of that - cutting the gap to :44 at one point, when it once again stabilized. It was only then that one could forecast with confidence that Sagan-Dillier looked to make it all the way.
only until Mons-en-Pévèle. I had a closer look at it yesterday, because in the post race interview Haussler mentioned that he just just missed the jump into that group because he was riding behind a rider who couldn't follow on the cobbles - that, in fact, was Burghardt
Sorry for the bad quality, but you can still see how G2 was established (Stuyven, van Aert, Vandenbergh, Debusschere and Phinney were ahead at that point as they already attacked earlier on - that's how they made the jump in G2):

Terpstra accelerates with Vanmarcke on his wheel (below the "45.6"), Gilbert closely behind. Van Avermaet in 4th gets out of the saddle to close the gap with a sprint, Bert de Backer on his wheel, somehow managing to keep up with him. Then we have Burghardt, Grondahl and Haussler. Haussler passes the young Jumbo rider on the right but gets blocked by Burghardt, leaving him with no chance to close the gap.
In the next shot (after showing EBH dangling at the back...) we see Terpstra, Vanmarcke, Gilbert, van Avermaet and de Backer together at the end of the sector. De Backer explodes immediately. Gilbert pays for his effort in the next sector. That's how G2 established.
Haussler said he had another try and came close to get back into G2, but then he had a mechanical and his race was over.