(it's) no wonder
It is not surprising or unexpected at all. You just worked a 20-hour shift? It's no wonder you look so tired. No wonder. This wire is completely frayed. I'm surprised the TV kept working as long as it did.
no wonder
[something is] not surprising. No wonder the baby is crying. She's wet. It's no wonder that plant died. You watered it too much.
no wonder
Also, small wonder. It's not at all (or hardly) surprising, as in With the goalie out with a sprained ankle, it's no wonder you lost the game, or If he finished off all of the turkey, small wonder he has a stomachache. [c. a.d. 900]
it’s no/small/little ˈwonder (that)...
it’s not surprising: If you walked all the way, it’s little wonder you’re late.‘The heating’s gone off.’ ‘I thought it was cold. No wonder!’