Yes, even back in the 80s and 90s, it was very common for European Students to use their student status to get visas to come work in the US for 6months or so, then take the rest of the time to travel and enjoy. They were a perennial thing at the Atlantic Beaches - but they were still largely a small, self-organized portion of the labor pool.
As labor got more and more difficult to fill, the opportunity formed for companies to work as brokers and work to connect employers with prospective labor pools recruited from Europe. Add in the fall of the USSR, and you saw the increase in eastern euorpean students too. The agencies actually go overseas, recruit, and interview people in Europe. The agencies help organize housing, visas, hiring, etc. The model becomes so effective that it has grown to include other seasonal help like lifeguarding - another market that used to be filled almost exclusively with local HS/College aged kids.
These people were not displacing workers - they were backfilling. Where the 'exploitation' comes in is how the companies optimize to cut their expenses. Poor housing, crowded housing, over promising, etc. But the employers are not getting 'cheaper labor' - they are having to pay more to get this to work.
It's pretty common now for the big employers in OC MD to have to offer housing opportunities to get labor in town because housing has gotten so competitive with organized labor brokers taking up huge swaths of properties (plus, the removal of many properties as old structures get torn down for new, higher priced RE development).
The students doing it generally love it as long as they get a great job. But a common complaint you hear is like.. being promised you'll work in NYC! Only to get here and be assigned to some podunk town with nothing to do, etc.
The plight is very much like alot of the agricultural worker need - importing labor became critical as people weren't willing to do this kind of temporary work.
