The significant environmental factor is that many planes have been sitting idle for months. This is exceptionally unusual in the life of most airframes. Idle time is an opportunity for parts or fluids to settle in a way they might not otherwise.

For example an extremely slow fluid leak could be “reset” every time the engine is operated. Allow time for fluid to accumulate and suddenly there’s enough fluid where it shouldn’t be, perhaps causing just enough mechanical stress to exacerbate an previously unknown wear point or design flaw present in a tiny minority of copies.

(Of course this hypothetical flaw couldn’t cause catastrophe on first flight, as that is generally an empty plane travelling from long term storage back to the airline’s hub airport. The flaw would have to subtly weaken a part which then fails after multiple rounds of uneventful flights.)

This was an elderly freighter, for which months of idle time in between owners isn't exactly uncommon in normal times. And in the case of this aircraft, it was actually acquired last year because the charter operator saw an increase in demand.

Unfortunately that hypothesis might hold true for all engine manufacturers which is a pretty chilling thought.

Or only affect engines from one American manufacturer due to some previously unknown peculiarity in their metallurgic processes.

I recall reading an article in Aviation Week maybe 30 years ago about turbine blades failing for an unknown reason, and it turned out it had to do with contaminates in the water they were using during engine builds or some such.

probably just as easily counterfeit aircraft parts due to economic squeezes