Most classical-specific instruments are just as much out of place in other genres as the cello. The oboe, horn, bassoon, viola, timpani, etc. The other instruments you mentioned have had illustrious histories outside the classical world for a long time, and the reasons for that are varied.

The mechanism for guitar is extremely common around the world (lute, sitar, mandolin, the Cuban très), so it's ubiquitousness in most genres of music should come as no surprise. The modern piano and synthesizer are evolutions of the keyboard layout from harpsichord, which has prominently existed for several centuries. The mechanism for trumpet is similar, with a history going back before the invention of valves, when you would just buzz into a fancy tube. The same can be said for violin and bass, although the classical double bass is pretty out of place in many genres today.

All of that being said, the cello is far from just limited to the classical rep. I would argue it's almost as common as the violin in pop music, especially if you count samples/synthesis of it in electronic genres.