Nino tends to suppress more over the Caribbean and GOM than it does out in the MDR or particularly the subtropical Atlantic. It's just that there's been a big expansion of the 26C isotherm both spatially and at depth over the last 40y (and especially the last few years) in these areas where a Nino won't really help stop development.
Obviously if you don't have a mod-strong Nino in place helping shear part of the basin, then this leaves open more area over time to higher SSTs and OHC. ENSO isn't the only game in town though, and changes to static stability via SAL intrusions and the West African Monsoon are important too.