There is speculation that antpool had significantly above expected luck to account for part of the jump.

Obviously some of the jump is from new (likely more efficient) hardware being brought online. Part of it could probably be explained by batch 5 (?) of S5's being brought online. Bitmantech had an unusually long production run for this batch of S5s so it is possible they were using some of their production capacity to build their next generation of more efficient miners and brought them online for testing/were mining for themselves. Another possibility is that a private farm built a lot of privately built miners with their own chips. I haven't been following the hashrate distribution closely but it looks like the "unknown" share of found blocks is very high right now and I would think a lot of the unknown found blocks are from corporate miners not mining on pools.