Yes, it does have to do with luck. Yesterday Hashpools luck was above 100%. Which is why you got a good payout yesterday. Today its down-trending. So you will see less now.
So the less Hashrates a pool has, the variation from 100% will be much more. Some days you will have an aveage luck of 50%. And other days you can see luck at 100%. This all plays out overtime. Hashpool has low hashrates compared to other pools. So its luck will vary a lot more. Also, its luck will average less than pools with more hashrate.
The good news is, If Hashpool can gain 10% of the networks hashrates, it will compete with the top pools like Poolfare. The more hashrates Hashpool has, the better it will perform until it reaches 10%. Further than 10% and its variation will be tighter, but not anymore better. This is the same as other pools like Poolflare.
You can see Hashpools average 24 hr. luck on the KDA page,