I'm here for all the questions because to understand how and why this is all happening you need to understand landscape and power players in European basketball.
One of them (probably the biggest one) is an agent of all these guys, think NBA Rich Paul but somehow more powerful. Petrovic, Mirkovic, both Ivisic twins are his clients, heck even Peja Stojakovic have connections to him. He also holds one of the biggest talent academies in Europe where he plucks players from that region (Balkans) and some from outside willing to come and work and compete in pro league against grown men while getting opportunity and minutes, something that is very rare for a young player in Europe to get, regardless how talented and good you are - your role will depend on how you produce against those grown men with plenty of things going against you not even counting lack of experience. Most of them just want an opportunity to showcase their game and no disrespect, most of them will come rather to play against guys their age than get bullied by older players and screwed on every 50-50 call against them.
Whats good for Illini is establishing some kind of cooperation with this guy, because he can get things done and fast. I'd look for Underwood to be a guest on annual coaching clinic organized in Serbia soon. Forging more connections with people there also helped Kentucky who got Petrovic's teammate from this season Andrija Jelavic commited (nice stretch PF with ball skills, fluid game and athleticism). Calipari was a guest there and less than a month later Zvonimir Ivisic commited to Kentucky to play for him. People are catching on fast but its good to get there earlier, think euro guys come kinda cheaper than portal players especially considering some money thrown around for players which really didnt showed much going around asking for some crazy $$. Ex-Yugoslavia is popular among them because they likely wont ask much, they've basketball culture on lock most of them are players with good fundamentals and it doesnt hurt thats place where one of the tallest people in Europe live. Average height for men where i live is something more than 6ft (I'm 6'6'' and yet im not even tallest guy in my friend group).