Gap between Seb and Lewis, before Seb's pitstop was 3.8sec. Gap between Lewis and Valtteri before Lewis's pit was 3.8sec. That is the gap they use to keep out of dirty air and just cruise around while saving tyres.
Then, Seb and Lewis pitted, both pushed for few laps to attack/defend from each other, and as last season that also affected the tyres. They realized that and started saving them, on top of that Seb had engine issues and Lewis had missing part issues.
So in the end, 21sec between Lewis and Valtteri is combination of tyre saving from Lewis, cruising from Bottas, missing part for Lewis. Which means, there is no way we can find out how much Lewis lost except maybe looking at fastest laps.
0.5sec faster for Bottas, he had newer tyres, no known damage and by Q he is 0.1sec slower than Lewis (to please Lewis's fans
). So he got 0.6sec with much better tyres and no damage. Knowing Pirelli, better tyres probably made more than half of this, meaning missing part could be 0.1-0.2sec, at most 0.3 as said above. Then we go through all the posts about Lewis, saying he is 0.5sec or more faster/better then Valtteri, meaning he should be able to overcome this difference. But, it doesn't happen and in the end we conclude that I just wrote a lot of text and didn't say anything.