A Tower Ground Control trainee reported several taxiing aircraft had to stop unexpectedly. The reporter did not stop one of the taxiing aircraft assuming they would see the preceding traffic but the aircraft crew did not see it as it was a smaller aircraft and they cut across the smaller aircraft's path.

Narrative

Working Outbound Ground; I had a Aircraft X ready to taxi off of gate X. They were instructed to taxi via 'X Y; Join X behind the Aircraft Y'. Then the Aircraft Y was just coming over the bridge and the next aircraft behind them was a Aircraft Z on Z just getting to A; which is usually more than a big enough gap for the prop to easily join without needing another traffic call. No traffic call was given to the Aircraft Z because I thought it would not be a factor. However; traffic on A came to a stop due to a push back off of Y and the Aircraft Y stopped just past Z. This meant Aircraft X could not complete the turn onto A behind the Aircraft Y; and was instead only half on A. When the Aircraft Z came over the bridge; they continued taxiing and either didn't see or ignored Aircraft X and taxied right up behind the Aircraft Y; cutting Aircraft X out and coming too close. Wing walkers were called out to ensure that the Aircraft Z could continue taxiing safely past Aircraft X.In my opinion; this event was a combination of numerous factors. First; in retrospect I should have anticipated the possibility of Aircraft X not being able to get fully established on A due to the Z push back and made a traffic call to the Aircraft Z. Workload; complexity; and frustration with construction/pilot confusion contributed to my attention being elsewhere. Additionally; there's normally a degree of trust that pilots will not allow themselves to run into another aircraft clearly getting established ahead of them. The Aircraft Z was far back enough that we would normally expect them to see the other aircraft and for it to be no factor; however; with Aircraft X being such a small airplane it is possible the Aircraft Z pilot didn't see them or saw them too late. If Aircraft X was a larger aircraft; it's very likely this event doesn't occur. I think the main lesson from this is to pay attention to irregular situations and understand that extra care sometimes needs to be taken when you have unusual traffic calls; like small props taxiing around much larger aircraft that may not be expecting them.