The only radical change was the addition of the all important anchor (<a>) link, without which the WWW wouldn't have taken off. [1]
Minor detail.
[1] http://infomesh.net/html/history/early/
https://archive.org/details/paulotlet
or google youtu.be Paul Otlet, visioning a web in 1934
biased incomplete list of link implementations pre HTML:
https://en.wikipedia.org/wiki/Hypertext#Implementations
The reason why WWW has taken off is very well described in:
High Stakes, No Prisoners: A Winner's Tale of Greed and Glory in the Internet Wars.
and has very little, if anything to do with the <a> incarnation, which as you say is a minor detail.
The only radical change was the addition of the all important anchor (<a>) link, without which the WWW wouldn't have taken off. [1]
Minor detail.
[1] http://infomesh.net/html/history/early/