That's the Congolese way. It are mostly people that artists are dedicated songs to and who are sung in songs. They want to show to people that they are close to the artist and their clothes. It started first from 70s with concerts at bars, where fans were coming on stage to make pics with their favorite artist when they were performing and giving some money. From then it became normal. Just look at all concerts of Wenge 4x4, JB Mpiana, Papa Wemba and Koffi Olomide made in Paris and Brussels you will see often people coming on stage.
Sapeur Frank Issekya profited from that occasion in 1999 when Papa Wemba performed at Forest National and holding Wemba's hand in the air, to use the picture later for his album cover Mokili Complique.