Correlation does not imply causation. I would propose that it is more likely that strong leader emerged who incited more mapping of such feature, or that community using that tag has grown or had extra imports/organized mappings, or that the improved semantics allowed more things to be mapped, etc - than that the mere tag name change (which majority of users rarely if ever use directly, but instead often use presets in their local language in their editing apps) has caused the sudden surge of usage.
But regardless, note that there were effort to handle old keys there. Maybe you weren’t involved in it, but it was there. So, potential proponents must be made aware of that fact that the “renaming of OSM tags” is much much harder and more time consuming than “search & replace” in their favorite word processor, which many of them seem to naively assume.
We replaced waterway=riverbank, landuse=farm… so how this can be a challenge anymore?
Have we really replaced (past perfect tense) them, now?
We have surely started the process of replacing them, and after mere 3 years of work we have made a great progress, but there are still
waterway=riverbank according to taginfo. Perhaps in several more years that effort will be completed, and those tags will really be replaced, but until such time, there is more fixing that is yet to be done to rectify damage that was done in the name of that “river modernization”.
But what is important is that this problem was considered, cost / benefit analyses was done and taken into account, and it was deemed that it will likely be worth it, and an effort has gone into proposing how to handle it in the best way. (and that is all that one would ask from new proposals!)
As we may deal with unifying tagging practices among many in use at the time of the proposal, consumers won’t be bothered by the change. They will continue to use existing tagging until it disappear from the database.
There are two types of data consumers: that which read data only, and those that write it too (AKA “Editors”. They both need to be upgraded, but possibly at different times (see especially bulletpoints 2 and 3 of this post).