Going by South American transfers outside of ARG/BRA, I think clubs can very easily drop a player they want of transfer complications, or that they end up having such a slow process that other clubs get the signing done before you even get in front of the right representatives. It's a huge advantage to have good relations with clubs, and to actually travel for the meetings. But yeah, very much possible in this case that scouts just didn't rate him that highly too, but there were like 8 clubs reportedly in for him at the time. There's a lot of bullshit you have to trundle through with agents from smaller leagues, it could end up costing a lot of money.
Re: contract, I think Brighton were the only team that actually got to the point where they had an offer accepted from clubs and reps, and a contract to sign on the table for him to sign. I remember following the Caicedo deal quite closely because I'd seen him play a few times and wanted us to get him.
It's definitely a factor that Brighton and clubs like them more often look outside Argentina / Brazil. That's why they have the established relations as well.
They expect to sell starters, and can plan a clearer pathway for emerging players, but the talents at IDV gets into the first team early, they regularly play in the Copa Libertadores and even made the final once (which is very impressive for a team outside of Brazil/Argentina), they've also won the Sudamericana (their version of Europa League) twice in the last 5 years, and Liga de Quito (Zambrano's team, also from Ecuador) won it this year, so there are plenty of chances to see the talents in established competitions that compares to experience in the Brazilian league, but yeah I'm sure it's factor. It's also easier to buy from Brazilian clubs. Most players from the Brazilian league won't cost ~40m like Vini either. Or €60m like Endrick cost Real Madrid when he was 16.