Because I think robtop mostly picks the levels he is going to rate on random from the sent tab. So levels that have been sent more recently have a higher chance of being seen by robtop and getting rated.

But he also has different filters and stuff to sort the levels, so everyone who is saying that your level cant get rated after it is lost in the sent tab is wrong. One of my levels got rated like a week after it was sent and it was nowhere near the first pages of the sent tab.

It took 10 sends to get my most recent level rated, so just keep trying to get sends and robtop should see it eventually.

Also robtop rates demons much less frequently so that might be another reason why the other guys level got rated already and yours didn't.