In other words.... cheap to modify.

Asking why the Trueno was more popular than the Celica is like asking why more people tune Civic Si's and SiRs than Preludes... and the comparison doesn't end there...

The Celica Supra of the time was already midweight with a big engine. The Sprinter/Trueno was lighter, with a small engine up front that, over the years, could be tuned and swapped with more and more powerful 4AGEs. You can do anything with that little four banger, turbo, supercharge, naturally aspirated tunes... anything.

And because it's always a small and light 4-cylinder in front, the Trueno maintains an excellent weight balance through all of this.