You mentioned just a few, and one of them (Kravstov) hasn't even really had any issue? He came over early and wasn't ready. That is not a surprise at all compared to his peers and it evidently did not throw off his development of his abilities considering how well he has fared in the KHL just this year.
Lias had some very real mental health issues. Deangelo is an entire other can of worms. There are many players that have done many worse things or had much worse issues throughout the NHL in the last few years alone.
It is just unfortunate. But frankly, our guys that develop well have far outweighed the number that have not in my opinion. We are still in the midst of a huge turn around in the organization. This offseason involved the final bits of changing over from roster staples that literally dictated the core, direction, and values for the better part of 2 decades.