The transverse Mercator projection is completely different than what people are complaining about. The UTM system is roughly what you get if you only take a narrow band of the ordinary Mercator projection near the equator, but turn the globe 90°, and use the projection for a narrow strip of a specific longitude, with a different projection for each strip, overlapping at the seams.

It was adopted by the US military between WWI and WWII, and similar projections were adopted by other militaries around the same time, because earlier (non-conformal) map projections led to dramatic errors when they were used for artillery targeting.

Maybe to be more precise, conformal projections like the transverse Mercator projection and the conformal conic projection were adopted by militaries after WWI, and the UTM system per se was created during WWII.