While the destination is always the same, the return path potentially changes with each hop, even on the same network. Traceroute, in its default configuration, bursts of 3 packets, with a Time To Live of 1. The first router they come to, decrements the TTL, and upon a TTL of 0, generates an
ICMP time exceeded in-transit message, which is sent back to the originating host, and the original packet is discarded. The traceroute program notes the IP of the router that expired the packet, and the time it took round-trip to complete that process. If for some reason, the router can't get a packet back to the tracerouting system... perhaps it has private IP address space; perhaps it doesn't have a route back to you (it doesn't need one; just a route to the destination, though this is unlikely), traceroute will display * * * after a timeout period has expired. There may be asymmetrical congestion that adds a few milliseconds to the path there, or the path back, but not both, which can decrease an interim RTT.
It's normal to see traceroutes like the one you provided, and there are a myriad of reasons for such.