Board Game Arena

I'm wondering how the number of Arena leagues gets decided for a given game. Is it according to player count and activity, or are other factors taken into account? As an aside, how are their XP rewards determined?

Some striking changes I've noticed while browsing through the Season 5 Hall of Fame:

• 7 Wonders: Diamond League dropped (but not in Yahtzee, with less players than 7 Wonders and only around 10% more games played)
• Abyss: Diamond and Platinum League dropped
• Draftosaurus: Diamond League dropped
• Martian Dice: Platinum League dropped
• Piraten Kapern: Diamond League dropped

And in Season 4:

• Dice Forge: Platinum League dropped
• For Sale: Gold League added (but less players and matches than Dice Forge)

It doesn't make sense, whatever they are determining. That said the whole league structure makes almost zero sense to begin with as it isn't mathematically sound.

Sushi Go is very difficult to get to Elite, but they haven't changed number of leagues. Troyes also hard and has very few players yet has a silver league for some reason (less than 100 players). Reversi would be easy to get to Elite even with a silver league but has only bronze and Elite despite 400 players. Terra Mystica dropped the Gold league and despite 1000+ players has only bronze, silver, and Elite (now since games are super long in TM this one I actually support).

7 Wonders had tons of players and was very easy to get to Elite, so reducing leagues was silly.

It seems the leagues were added back to Draftosaurus, Martian Dice and Piraten Kapern. Or there could have just been no players in these leagues temporarily, but I thought they would still be shown with a player count of 0 in that case.