I think being 2weeks since July 24th we can conclude that the spike was not random network variance. The 10% spike was most likely new ASICs going online. The 10% gradual increase in the past 10 days was perhaps other algo users switching to ETH as their algos fell to ASIC (which is ironic since ETH is no longer a GPU haven).
Anybody mining ETH right now on GPU either has dirt cheap power or is mining Hopium because the cards like the 1070 and the 1080 are depreciating faster than the value of the ETH they can mine. Even Ryzen 2 CPUs are tanking in price with Ryzen 3 CPUs spanking everything.
Looking at
https://etherscan.io/chart/hashrateIt doesn't seem like a huge spike. You might be right that its some new ASICs however there is also the possibility that the people who bought GPUs in 2017/2018 are powering their rigs back up again since Bitcoin and Cryptos seems mainstream again.
If those people sold GPUs back in 2018 then most likely there are other people who started to mine right now because they are expecting ETH to go to $1400 again. Many people think this because it looks like BTC might go back to the $20K ATH and they feel that ETH will be no different.