The world knows that BPL and global T20 was going to clash. Now these leagues are affected by the participation of international quality players. As of now, BPL seemed to have been doing an excellent job for some few specific reasons.
A good number of WI players like Narine, Lewis, Simmons are all expected to play the BPL. Most of the top tier Pak and Lankan cricketers are signed up by BPL teams. Now a certain Malinga is playing in the Global T20 though. A lot of T20 specialists like Rossow Luke Wright Lynn in the mix too.
Its likely that players would have loved to participate in a tournament in SA even if the pay in BPL is better. However, since BPL allows players to be signed officially even before the draft, it allows for foreign players to be booked beforehand. And these players want that sense of security, security that they will be participating in BPL no matter what. It maybe such that a lot of decent cricketers miss out on Global T20 selection.
I hated the idea of selection before draft but looks like its a blessing in disguise