Do you have the 2 speed installed or is this more of a general question? If you have the two speed I’m thinking the shift servo may not be set correctly and the shift fork could be binding on things when it’s pushed too hard causing additional resistance. If not see the next paragraph.
Improper gearing or high drag in the drivetrain are the likeliest causes. Are you running the stock gearing? If you put a larger pinion gear on to make the truck faster you may have overdone it and are burning up motors with too much load. If the gearing is stock or lower than stock
I would start by removing the motor from the plate the rotating the axles or rolling the truck across the floor. It should spin pretty freely with little resistance. If there is significant resistance try removing the driveshafts at the axles to isolate where resistance is, then fix the bad bearing, bent axle shaft, front CV, or something in the trans/transfer case.
Which motors are you running as replacements? I’ve been running my Bomber with the lower ratio axle gears and 2 speed trans kit off a cheap Traxxas 21T 550 motor for years on the stock ESC with zero motor or speed control issues. I purchased a Holmes Hobbies brushed motor for my TRX-4 for about $25, it also works fine.
https://www.amazon.com/Traxxas-Tita...GPX59MKR5KT&psc=1&refRID=46ZWXEESMGPX59MKR5KT