Sounds like it's more or less in line with previous Finals:
Just like the Olympics gets good ratings but nobody is watching track and field outside of that.
All-time World Cup Final among most-watched soccer matches
An all-time FIFA World Cup Final delivered one of the top soccer audiences ever on U.S. TV as Argentina-France topped 22 million viewers.
www.sportsmediawatch.com
On a linear basis, the World Cup final ranks fifth all-time among soccer matches in the United States behind the match window figures for the 2015 Women’s World Cup Final (USWNT-Japan: 26.7M), 2014 Germany-Argentina men’s final (26.7M), 2014 USMNT-Portugal group stage match (24.7M) and 2010 Spain-Netherlands final (24.3M).
Just like the Olympics gets good ratings but nobody is watching track and field outside of that.