I think of them like scratch off lottery tickets - but you play the machine and that gives you the result, you don't have a physical ticket.
So like with scratch offs there's a whole pile of tickets for each type of ticket that has winners in various amounts and losers. Whereas scratchoffs have maybe 10 or 12 different payment possibilities, VLTs have 100s or 1000s of possibilities. Each spin on a VLT takes one of those "tickets" out of the pile, then the reels tell you what you won.

I play at both racinos and casinos. VLTs "feel" way less random. They seem like they either pay or they don't, and by pay I mean any win however small, and that can vary based on the bet size at the machine moreso than it "feels" like they do on regular slots. So it's almost like they sold all the winner tickets already and are just trying to get rid of the losers. Whereas regular slots are just working with the RNG with an overall payout percentage behind it, so it's whatever the RNG decides to dish out irrespective of what specific amounts have been won before.

So I don't think your observation is so much that those banks that are winning is so much that that bank was picked to win. But rather that, to use the lottery analogy, there are just more winners in their pile at that particular point in time than there is in the pile for your bank of machines.