Although known for a long time, the London started to catch up in popularity just in the last decade or so. 

I guess the reason for this is probably the desire of many players to focus more on the practical side of chess, with less use of engines and less memorization of long theoretical lines, and more about positional understanding of game. I must say, it received a huge boost not only in the number of games but also in a deeper understanding of the positions arising from the opening. In the past it was used from time to time, but only a few players employed it on a regular basis, such as grandmasters from former the Yugoslavia, Milorad Knezevic and Vlado Kovacevic, and the English GM Tony Miles, who used it often. 

Today, Kamsky is one of the players who uses it very often, and of course Magnus Carlsen, but we have many other grandmasters and non-grandmasters who now have it in their repertoire on a regular basis. I must say that it’s also important to emphasize the move orders of the line, and due to that we have an immense number of transpositions, which you don’t find so much in other openings.