Is it really a trend? I would call it more of an experiment.
I haven’t heard of pro tour road riders going to anything shorter than 170mm cranks, with most still using 172.5’s. I still believe most world cup mtb riders are using 175’s. But whatever works for you, go for it.

The wide handle bar rage is simmering down a bit though. I still ride 800mm bars on my enduro bike and my new XC bike came with 760mm, which I’m thinking of trying 770mm or 780mm bars. I Although I didn;t think I’d like the wide bars, I actually got used to them and like them.

The trend is toward shorter and shorter cranks even for taller riders. Apparently even pro tour road riders are trending significantly shorter due to new research. It could be like 810mm handlebars though, every pro seams to have slowly shifted back towards ~760mm, so in 5 years everyone could be back to 170 or 175. I have short legs so the proliferation of 165 cranks has been great for me.

I agree with running shorter cranks on long travel, mostly gravity feed bikes might be the ticket for some.
I used to race downhill and used 165mm cranks, but then back up to175mm cranks because I rode faster with them in the pedally sections of some DH courses in which I excelled at.
Even on my Turner RFX which has a notably low BB height, I use 175mm cranks. Yes, I may get more pedal strikes every once in a while, but the stuff I ride mostly, 10mm of crank length isn’t going to solve the pedal strike issue.
CC make the eeWings in 175mm, just wondering why they didn’t offer them in this finish.

That’s funny, most riders I know on MTBs run 170 and 165mm cranks. 175mm cranks usually equal pedal strikes.