The F-104S TAF had the highest efficiency at 10.7, therefor it was not possible for it to remain at that BR. Any vehicle that's at the very top of its given BR bracket is subject to being increased. Its also worth noting it could face all the same vehicles that it faces now, with the exception of the lower 9.7s it outclassed which it previously could but now cannot face.
As its only been a single day since the changes, its too soon for any reconsiderations of BRs at this time. However the developers will monitor the changes to all vehicles and take them into consideration in the next BR update.
Me also personally playing a vehicle is not how vehicles BRs are decided. But I have indeed played it tonight and extensively before the patch too.