Because before Cuba got tons of oil from Venezuela.

The US ended that with no plan on how Cuba would cope, just left them to fucking die. It's gross.

Cuba had it's entire infrastructure built around oil burning to produce power.

Yes, optics, because if the US sinks ships carrying solar panels they lose even more respect on the international stage and bring even more attention to their illegal military blockade of Cuba in which they have directly killed over 200 civilians via bombing vessels in and around Cuba, and indirectly killed at least a few thousand by eliminating oil imports to the country.

China had nothing but risk before the carrier group was moved into place, as the US' official stance was international sanctions and complete lockout from using USD internationally if you dared to trade with Cuba.

After the blockade those sanctions are meaningless as no other country would follow the US if they actually issue said sanctions, and the US itself isn't economically capable of handling sanctions against China at this point in time. So China has no risk to help out.

Because before Cuban doctors didn't have to rush to manually pump the respirators for intubated infants multiple times a week during blackouts due to the US blockade intensifying.

Literally every good thing countries do that they don't have to is either completely or partially optics.

Maybe, but helping a people with similar politics who are suffering miserably is always a good thing for those people. The fact that they are so close to a mutual enemy is icing on the cake.

This is the culture that gave us "the Art of War", after all. I'd expect no less of them, and normally I'd expect at least as much from us. Unfortunately we're lead by the (possibly) worst representative of humanity possible right now.