I am ont saying that all of them, do. By no means. There are plenty of top draft picks that went on to have great careers in the NFL, but there are just as many who are 1st or second roud picks who end up out of the league in a fairly short period of time.

My personal opinion is that this happens for a few reason:
1. The NFL is so much better than college, that it is just really hard for QB's to be able to make that next step and be successful. Because of this, and because teh criticism is so harsh, gusy that don't have it are ushered out in pretty short order.
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Second, I think where a QB goes, the situation he is in, and the coach he has is a huge factor. Trevor Lawrence is flirting iwth staying in the NFL because he does nto want to go to the Jets, who have a broad reputation as a terrible organization. I think this is the case for a lot of high dfaft pick QB;s. They almost always get drafted by teams that are in terrible shape. And so they are drafted by a certain HC who likes them, but that coach is fired and in comes a new regime and that drafted QB, who struggled does not fit into the new coach's plans. John Beck talked about this very tihng on Criddle's show.

3rd. The NFL is all about measurables. And the QB is the one position where the non measurable attributes matter just as much. Certainly a QB has to have at least an NFL arm. Teams are just too fast nowadays. But we've heard for years the NFL wanting the prototypical QB, who checks all the boxes. But, the QB, unlike other positions on the field, has to have those intangible qualities that often are not measurable until they get into the NFL.

Well those are my thoughts anyway.