There is a lot of good that can come from this move. 1. The UN has been criticized as a notoriously Western organization. Moving more functions, especially something as globally impactful as UNICEF, to Kenya can signal a push towards giving the Global South a larger voice in the organization.
2. $300M+ investment is nothing to sneeze at to improve Nairobi infrastructure. On top of this, the salaries of UN employees moving to Nairobi will largely feed the local economy, bringing external money into Kenya to help boost the economy.
3. Symbolically, as the article points out, this puts Nairobi on par with Geneva and NYC, making it the first non-Western hub of such for the UN. It shows that Africa has a seat at the table and acknowledges the importance of Kenya as a leader in the African continent.