co-occurrence, conjunction, concurrence, happenstance, coincidency, coïncidence, quincidence, coinciding, coincider, cooccurrence, more...

intention, design, plan, purpose, deliberation

synchronicity, serendipity, chance encounter, fortuitous event, lucky break, twist of fate, happenstance, fluke, more...

mere, strange, curious, remarkable, happy, singular, pure, odd, sheer, extraordinary, interesting

chance encounter,   chance meeting,   situational irony,   happening by chance,   rare chance,   accidental meeting,   small miracles,   it's no accident,   sheer luck,   accident of chance