How is Tommy Tuberville able to block Navy and Air Force confirmations?

The Senate passes these appointments in groups. Any Senator can object.
Each appointment can be approved individually, but that takes a lot of time.

The system does not work well when very low-quality people get elected to the Senate, particularly when blatant misbehavior doesn’t end up having enough consequences.

it doesn’t make any sense to me.

He heads the committee that can do that. He decides when nominees can receive a vote.

NPR has a pretty good explanation