I think NASA helped fund it because they wanted more (And more reliable) data to a groundstation on the island, not because this subsea cable is anything special.
Fibre optic is great because you can usually add more bandwidth by lighting up another wavelength. The amplifiers don't need to be substituted if the wavelength is within its range.
Actually we know that a single mode fibre (there would typically quite a lot of them in a cable) can carry around 100 Tb/s in the C band (used by most systems due to amplifier availability) over about 100km. Research systems have reached that limit and commercial systems are not very far off.
For the super high capacity demonstrations, 256 QAM and/or probabalistic/geometric shaping is typically used so we get to about 12 bit/s/Hz (accounting for FEC and pilot overheads). Interestingly, data rates are mainly limited by the transceivers (RF amplifiers, DAC/ADC ENOB... is not that great at 25-100GHz, which is required for the 50+Gbaud symbol rates).
OS2 single mode fibre is pretty future proof. The transceivers may change, but the underlying cable should last a looong time and can be sliced and diced considerably with WDM (16+ channels AFAIK).
Fibre optic is great because you can usually add more bandwidth by lighting up another wavelength. The amplifiers don't need to be substituted if the wavelength is within its range.