Obviously there were other choices. But large investment fund managers now mostly operate on the FOMO principle. They don't want to look stupid by missing out on the next big thing. But if they take a loss then they can explain it away because "everyone else was doing it".

At a more fundamental level, this is just another example of the principal-agent problem. Pension fund managers optimize for their own careers rather than for the financial health of retirees. This is one of the reasons why all defined benefit pension plans should be eliminated and replaced by defined contribution plans.