Why does Amazon favor my competitor?

I have been a seller on Amazon since 2010. My listings have always remained at the top even with competition. This past few months, one brand in particular has been surpassing my listings within a few weeks. They have overall pick less than 100 revues to my 2000 revues. They are selling equal volume or more. How is this possible, has Amazon changed its algorithm? They seem to favor this seller more out of nowhere.