Big odds are visual way of marketing casino and that's what stake is doing. If you want to see more about this odd changes, whenever there is high interest in a particular game like the way Arsenal and Real Madrid are coming, some casino gives big odd in anticipation for people to come bets on their platform because other betting platforms will be having them, to snatch players, they use big odds to attract players and it reduce as the event comes to time.
This particular screenshot was share like 3 days ago, tomorrow is the day of the match. If you check that game today, the odd would have decrease but if it happen that there are no interest from bettors, the can even increase it further and then change it immediately they amass huge number on that particular game, that's how bookmakers play their book and put the casino interest before anyone. The day of the game, you might see that reduced to 1.2 odd for Real Madrid.
You should see Super Bowl odds, in most cases the odds are so crazy that, it is very unlikely for someone to not make a profit, so you wonder how the oddmakers make a profit, but the reality is that it's a "bait" bet for the sportsbooks.
What this means is, back in the day, when Walmart first started, they sold bread and milk for nearly free, basically they were making a loss from those two items, but those two items are things people need everyday, so they made people come in, shop, and yes Walmart made a loss from those, but then when you went ahead and bought other stuff, you made a profit, because people came to your Walmart for bread and milk which was cheapest, they bought other stuff there too.
Same logic here, Real Madrid and Arsenal odds could be great, could make you join their website, and even the bookie could make a huge loss from that, but then in return, they would gain plenty of customers who will later lose that money back to them.