It's quite crucial to point out that Tim had a solo at a time that even Azreal was able to have his 100 issues run.
It doesn't mean that Tim isn't a great character or that his run wasn't good, but at that time it was much easier for sidekicks or other characters to have long, successful runs than it is now.
As for DC's strategy to rely on Tim's fanbase that believes he's the best Robin, I'm not sure this fanbase is as big as they hoped.
While Tim's DC pride story sold very well online, it apparently sold very poorly in stores and didn't even make the top 100 -
https://www.comicbookrevolution.com/...ales-rankings/
Same with YJ 1. A debut issue and a Dark crisis tie-in, that focuses on the original gang, didn't make the top 50.
While ICV2 ranking isn't perfect, they do raise a very concerning picture regarding Tim's popularity and the success of his new solo. Especially as these issues were written by the writer of his solo.
So while I'm sure there are Tim fans who are eager to read his new Robin series, distancing the fanbases of other Robins (that may like Tim but still don't consider him the best) really isn't working to his advantage.