For many countries, the decision to allow visa free travel is based on the likelyhoodlikelihood of abuse of the immigration system. In the case of MauritusMauritius, the judgement is that Mauritian citizens do nonot represent a significant risk of overstaying. Mauritius has a stable democratic government and a successful economy, so Mauritian citizens are happy to return home. On the other hand, Mauritius is not so rich that it feels the need to protect itself from immigration. It is happy to allow visa free travel to encourage the tourist industry.
Mauritius has a diverse population, with links to the UK, France (former colonial rulers), India and China (significant demographics). It has good relations with the superpowers, and has benefittedbenefited from this.