Instead of giving away it all away, why not invest $8B which would generates about $800M per year in returns perpetually and give that as 0% loans for education

Instead of giving away it all away, why not invest $8B which would generates about $800M per year in returns perpetually and give that as 0% loans for education, health and starting new businesses to people who needs it? This would be then perpetual giving that can outlast the donor.