These kind of association between a celebrity and a Cryptocurrency company is simply to drive visibility, which is not bad at all. The same applies with any other brand out there. Often, brands may choose to sponsor football clubs or major football events. By collaborating with football teams, these companies gain visibility and promote their brand within the football community. For example, a popular cryptocurrency exchange may choose to sponsor a football club's jerseys or stadium, displaying their logo prominently during matches. I am yet to see the video though, but if Messi, the GOAT is openly talking about the exchange, then he must have a level of trust for them to give such level of exposure.