How did Bitcoin clear up it's mempool so quickly today?

Does anybody know how or why Bitcoin's mempool got cleared up today in an instant? 

Bitcoin's mempool clears up almost instantly

Also, Bitcoin Cash's Difficulty Adjustment was easier than normal today so it should have worked in its favour. Why then was there more hash power being diverted to the Bitcoin network. 

Hash went to Bitcoin

Any explanation or link is very much appreciated. Thanks. You can use the contact form here if you don't want to post a comment publicly.