I don't imagine that the people over at Hyundai Motor America have a hard time with English. This was merely not knowing/caring until it became a problem.
Not saying Hyundai America doesn't listen to Hyundai Global, but if they have to wait for Global to pull an ad then there are some serious management issues.
By that exact metric Twitter is declining. Less twitter users, less engagement, less return on investment for ads on the platform. That said, the decline is only something like 360M to 330M over a few years, not a huge deal.
A caveat to this is most ads go through an automated bidding process similar to Google's advertisement, and the companies only pay per ad seen by a user.