Under What Specific Condition Is an American-Style Call Option Most Likely to Be Exercised Early?

An American-style call option is most likely to be exercised early just before the underlying asset goes ex-dividend (or the crypto equivalent of a major airdrop or fork) when the option is deep-in-the-money. The holder exercises to capture the dividend/airdrop, provided the value of that payment is greater than the remaining time value of the option.