The ones that were accepted quickly could have been decided by the ML (machine learning ai) model that Niantic uses. Those emails will say the decision was from “our team” instead of the community.
Wait times in queue and in community voting vary widely depending on how many reviewers are active and how many explorers are submitting in your area. You can help clear any backlog by reviewing yourself. You can earn upgrades from reviewing which you can apply to your nominations to send them to a wider review pool, which usually means a faster decision.
If you want feedback on a rejected submission, I would suggest posting it in Nomination Support
There is a daily sync when accepted Wayspots which are eligible to appear in Pokemon Go are added to the gameboard.
I know the prompt tells you that you are submitting a “Pokestop” but you are actually submitting a Wayspot to the Lightship database, which can only become a Pokestop or gym if it is alone in a level 17 S2 cell. This is a good article about S2 cells and PoGo: https://pokemongohub.net/post/article/comprehensive-guide-s2-cells-pokemon-go/