How can I show the results of my poll only after everyone has voted?
You can choose to reveal the full results of a poll only after the poll is closed and no more votes can be added.
To do that find the Show results option under the Settings section during the creation of a poll and select After closing.
Up until the poll is closed, a respondent can see the votes they cast and change their vote by clicking the Show my votes button located at the bottom of the posted poll.
Once the poll creator closes the poll the full results of the poll will be revealed and visible to everyone.
If you are creating a poll using the /poll command, you can add the keyword show-results-after-close to enable this setting: