because for example they had projects to come to europe even for studios and have strong security around like fally was doing to still have some studio and concerts but then in both groups there was "what if these new guys run away" and from then the number of african concerts started reducing in both groups,my uncle who used to be a promoter who i talked about years ago always used to say that even taking a group to europe for shopping gives you an advantage compared to the one who only toured in africa in terms of negotiating a higher contract
and in the case of ferre especially,part of his issues to bring more members to europe come from the fact the last europe tour he had before restarting was the one that saw michel synthe,jus d'orange,patou and co leave,and in this cases unless you play up to the authorities to build a storng relationship of trust you have big chances of having to pay for it so that was nearly 15 years without ever applying for visas
i dont know if you remember at some point tresor was saying around 2016 2017 that him marchouse and a couple of guys like 6 7 were meant to come for polemic reasons but to build contacts aswell for when concerts would be back,but then ferre backed out and preferred waiting for when he'd have concerts one day
and ever since every single artist who has had comfortably over 20 visas had to pass by the one who maintained constant relationship with french authorities and bow down
maybe both of them making europe moves earlier than that would have keep the "star making" system in groups alive,now there was still some little curiosity around like seeing say rhize in europe for the first time or jamaique,but that was different hype from the past because this culture has been allowed to die a lot