The Shermans were powered by 4 types of powerplants. The M4 and M4A1 used the Continental radial engine, the M4A2 a twin GM diesel engine, the M4A3 a Ford V8 and the M4A4 the Chrysler multibank. Production numbers mattered so it was a question of making best use of what was on hand. The multibank M4A4 was the first one to stop production in 1943, a victim of rationalization to eliminate the most complex engine when sufficient others were available.
The US kept most of the M4, M4A1, and M4A3 models for themselves with the M4A2 and M4A4 being provided to allies on lend lease. There was some theoretical advantage to the M4A2 diesel as diesel is less volatile than gas in a fire. 50 yrs ago I learned to drive a M4A2 diesel and it was quite an experience. When I was in Argentina a couple of yrs ago I was surprised to see an M4A4 preserved as a monument outside the military HQ in Buenos Aires.