The article says that the Islamic Revival started in the 1970s, then uses Hajj attendance numbers between 1926 and 1979 as evidence.
Why the incongruent dates? These 2 datapoints say nothing of the changes between the mid seventies (when we are told this revival started) to the present. A second problem is that durind this period international travel became become more accessable to millions of potential Hajjees.
TL;DR The Hajj numbers have confounding variables and the time period makes them useless.