Plano,

There are probably better explanations but here's one. The G major leads to C minor because you have two notes moving up in half-steps and a common note.

The B note of the G chord moves up a half-step to the C.

The D note of the G chord moves up a half-step to the Eb.

The G note is in both chords.

Moving up a half-step is so common in Western music that your brain has been conditioned to expect it.

Hope this helps.

2b

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