The placement airlines paid for them. Placement from the outset did not guarantee anything (whatever might have been assumed,) but the result was the offer of full time contracts. Obviously for the candidates this is the best possible result. The airline gets what it wants. The candidates get what they want. The FTO gets what they want.
easyjet is a different company with their own requirements. There are a number of pilots who are moving from there to companies now offering better terms and conditions. That is an option available to some of them, and that is their choice.
The FTO, in an ideal world, would want to see all of their succesful graduates move on to airline placements with the partner airlines. It would want to see those pilots achieve full time contracts at the end of their placements. This is their primary business model. Unfortunetaly it is not an ideal world, and given the obvious economic realities of the last five years, they have had to adapt their business model in order to keep some throughput in this market.
This adaption of the business model is also what many of their partner airlines (and many who are not partners) have also done to ensure survival.
In some cases the results have been far from ideal, but they were very likely the best that could be achieved in what has proved to be an incredibly difficult marketplace.
This same period has seen a backlog (holding pools) of graduates for whom placements cannot be seamlessly found. easyjet provided a relief valve for this backlog since they were one of the very few companies expanding in this market. Nevertheless that relief came at a price. With almost monopoly demand during this period, they could (and did) adjust the terms and conditions to suit their own market position. The option was (presumably) to simply say no, and buy on the open market. That would have been experienced pilots on whatever T&C's that market would stand. Some people would undoubtably have preferrred that, however a deal was achieved that clearly was a compromise for all parties, but nevertheless served to keep this route open through difficult times.
As more buyers (airlines) come back into the marketplace, so the T&C's on offer become more varied, and options become less limited. Guarantees, promises, and certainty, just doesn't exist I am afraid. It not only doesn't, it never has! There is a large element of risk. That risk needs to be understood by anybody considering assuming it.