They bought into the FOMO.
Anyone with enough sense and trading experience would have seen the collapse coming. So, I do not feel for the people that got in that
Yes, they were naive noobs.
Once the proverbial horse has bolted, there is little chance to catch it ie. once the initial spectacular, easy gains had been made, you could no longer just make money HODLing.
HODL (first person): 'Hold On for Dear Life', 'left holding the bag', to invest and never withdraw;
HODL (second person): taken the profits and got away, stole investments of HODLers.