Why didn't I receive any curation or only 0.001 Steem as curation fee?
While I did upvote before the whale....

Recently I received this question. To answer it I will look at it from 2 perspectives. But first some details from the specific post that triggered this question.

For this post I only got 0.001 SP curation reward: https://steemit.com/blockchain/@swissclive/blockchain-taken-down-by-bots-all-crypto-gone-programmers-rush-to-wind-back-the-closk
Total post value ended at $300. My SP was about 75 and I upvoted after 30+ minutes when the post value was close to $30 (at least if I remember well).

My historical curation rewards data table

When I had 15 SP I created a table with my curation rewards. The following picture shows part of that table.

You can quite easily see that if you upvote as 1st you get by far the highest curation reward. And that it quite steep decreases. And that it quite soon becomes zero, which is shown by the last two lines.

Of course this time I had 5 times as much SP and the post reward was much higher. So my historical data won't help us any further then informing that the curation reward decreases pretty quickly.

curation from your own vote

Let's assume you are the only one to upvote a post or comment after 30+ minutes. That means you will receive the full curation reward from your own vote.

My vote had $0.02 value back then. So the curation fee is close to $0.005. And with a Steem price of $4 that results in 0.00125 SP curation reward.

Then we go back to the quickly decreasing curation rewards. We use this brilliant post to determine that if a post receives 4 equal upvotes, only the first upvote receives an higher curation reward then it's own upvote value.
https://steemit.com/curation/@miniature-tiger/an-illustrated-guide-to-curation-from-the-simple-to-the-complex-with-real-examples-from-past-posts-part-1

As the second upvoter already received much lower curation reward then its own upvote value, I estimate that 85%-90% from the upvoters won't receive a curation reward that is higher then their own upvote value.

The post I upvoted ended at $300. My upvote was around a post value of $30. So that means I'm somewhere close to the 90%. And I will never gain a curation reward that was above my own curation reward value of 0.00125.