It is amazing to realize how much aircraft changed from 1920 to 1940, and how difficult it was to properly train people to operate the new ones (all the way to stop).
A "ground loop" means exactly what it says, a very sharp turn from your intended path. Your mechanic would not be happy when the cost of damage to struts, wheel bearings, tires, and other items (should a wing drag) is assessed.
The ground stability issues of these new planes came from 4 sources, greatly increased engine power, greatly increased weight, and, especially for this discussion, weight behind the brakes of the main wheels, and the natural "weather vaning" tendency of a directionally stable airplane.
The fourth is an issue of decreasing rudder authority in a crosswind rollout that has never changed. What did change was putting a wheel on the back instead of a skid, and the relatively larger vertical stabilizer on the newer low wing monoplanes as compared with biplanes. Having a narrow track on the front, such as the Me-109, made the differential braking required to control this more difficult. Wider track mains helped.
Greatly increased power lead to much greater turning tendencies as throttle was applied, and the greater weight per area meant inertial "overshoot" with inadequate aerodynamic control became more of an issue (should be ringing bells for you "Dutch Rollers").
But the fundamental problem is brakes in front of weight. Tractor-trailers are famous for "jack knifing" for the very same reason. A fully loaded tractor trailer has 60% of its braking in front and 75% of its weight in back. This is why it wants to "swap ends" when brakes are applied. Very similar concept to drag and weight in the air (the parachute). Drag wants to be in back, weight in front for a decelerating object on the ground.
This conflicts with the need to have the mains "raked forward" to keep the plane from flipping forwards when landing! Which brings us to the old term "tail dragger". When older lighter planes landed, the skid in back would more stably drag it to a stop (from maybe 35 mph). Newer planes, landing at 100 mph, with brakes on the mains, were a different story.
The tricycle gear greatly helps this issue because the mains are set behind the CG.
The "tail dragger" concept was successfully applied to the X-15, which followed the bi-plane tradition with 2 skids in the back and a wheel in the front. The Space Shuttle was a trike.