1. Bottas had to go a much shorter distance on the C3 and was going up against a C2 that had already done a good number of laps.
2. Bottas was never quicker than Hamilton on the C2, even though he had to run them much shorter and thus could have pushed them harder. So Hamilton went much further on the C2 than Bottas did and was quicker than him on that tyre for almost the entire stint. So much for Bottas's speed and tyre management skills being better than Hamilton's.