This misses some vital data. Firstly that without a measure of availability it’s easy to climb the rankings by simply not offering service to people outside of cities.
Extending coverage of broadband to rural areas will lower a nation’s average speed.
Secondly - many people (in the U.K. - most) buy on price alone. They’ll buy the cheapest available service which won’t be the fastest.
Measuring in this way doesn’t tell you anything about how available broadband is and it doesn’t tell you how affordable it is. A country that has a single 1Gbps broadband service available only in the capital city for $300 a month and only 100 people subscribing would top this table.