Veteran players play in BL because they have better chances for taking prices. In BL there are half not skilled players that would play any card they draw in their hands without thinking and they usually use 1 deck copy-pasted from veteran players posted on forum.
This is my first time playing league, actually I started being active on forums when I started playing this league. And didnt knew how things are going. So now when I know, I will certanly if I take 30 matches in next season go in BL, reasons:
1. More players -> more matches -> more fun
2. Half number of that players are newbies, so half matches will be easy win -> better chances for taking prices
3. Metagame is on high lvl because of unupped cards, you can combine every card and put in your deck, so there will be a lot of different decks and that is in my opinion beaty of elements. In CL we all use 2 or 3 same decks: poison, rainbow and sometimes rarely seen it appears third deck, but that is really rare.
So I think the only solution for next season is to put in rules: Players with more than 50 000 score cant join BL.
With that rule, in both leagues would be approximately same number of players and it would be really balanced : Let newbies play against newbies and enjoy in some winning and veterans play against veterans. That would be pitty for me because I will never see BL
but both leagues will be active.