In 2000 some basketball clubs split off, made another league and FIBA was furious. FIBA managed to keep only 3-4 top clubs so basketball was split between the Euroleague (which had most top clubs) and FIBA's Suproleague which was the poor relative. After 1 year FIBA scrapped the Suproleague altogether and only the Euroleague remained. The Euroleague has been running as a closed league since then.

International basketball leagues in Europe are a mess, they went through several schisms and, if i remember correctly, some of them now work on an invite basis. You can reach the top rings of a national league and still don’t get into the European competition you’d deserve simply because you’re judged “not big enough”. The contrast between our system and the NBA has always been stark, but at least in the past century this could be justified by a love of competition; now it just shows that the European game is run by amateurs and bureaucrats.