How to analyze competitor's traffic source?

Hi guys,

There is a competitor who went from 40 to 500 visitors per day over a period of a month (according to SEMrush). That happened at the beginning of 2014.
Is there any way to find out what was there marketing/seo strategy 1 year ago?

Monitor competitor website traffic strategies involves with social media networks. See how your competition carries out their social media engagement.