Trying that tantrum on is likely instinct.

Learning it works if you escalate far enough is 100% learned. Maybe purely operant conditioning in babies, but there is also intentionality and cognition at work in toddlers' tantrums.

My boys were never indulged for tantrums, so they stopped at 2. Friends' kids I've babysat ARE indulged for tantrums so they continue. Until the second time I babysit them, then they just grumpy but respectful until mummy and daddy are back.

Tantrums are the parents/caregivers fault.

Always.

But its usually fixable up until about the age the kids start to vote.