Here an nice article that does some analysis in regards to this problem: A date with Sybil.
Classic nodes went up 1300-1400 in a day. You saying 1300-1400 people brought nodes online all at once? 
Not saying it's impossible, but pretty unlikely. There is someone now boasting on reddit about owning 800 nodes in the cloud, paid through May.
All their nodes are controller by less than 300 people. Not saying it's impossible, but pretty unlikely. There is someone now boasting on reddit about owning 800 nodes in the cloud, paid through May. 70% of hash power is controlled by 3 Chinese people whith whom Blockstream/Core signs backroom deals.
This is not a problem at all because no one node control more than 30% of this hash power. Expect that you think chinese people act like zerg. What will you say if the same power controlled from white people in Zurich or in Usa? I am very sure that then you will have no problem with this situation. To find a centrilized mining problem look to any other altcoin not to bitcoin. For example in ehtereum one single node has 49% of hashpower atm.
The logic of the Blockstream/Core supporters: a concentration at 300 people is a problem - a concentration at 3 people is not.