That page doesn't say banned, it says most of them never had it in the first place. (It also indicates that the multi-use flu shot vials still have it, which further refutes the 'banned' wording.)

The likely reason it was removed from those that did have it was "people are making a fuss about it, why not remove the ammo even if it's harmless?"

No insights that I can support. My long-unrefreshed impression of thimerosal after looking into its toxicity as a vaccine preservative is that it was statistically insignificant. Impression not informed by data later than about 2005.