You build a team’s confidence by giving them wins they actually earned, not ones you handed them.

Confidence built on handed-out wins is thin, because people know when something was given, and the next real test exposes it at once. What produces actual belief is succeeding at something that could have gone the other way, which means the difficulty has to stay in. Protecting somebody from the chance of failing also protects them from the evidence.

Give somebody a task genuinely hard enough to fail at, and let the result be real. Help them prepare rather than smoothing the path. Then point at what they did instead of what you did.