One of the potential mechanisms of action of Vascepa is as an anti-inflammatory. But that is not the only potential mechanism. Like apabetalone, there may be many beneficial mechanisms all happening simultaneously. From the Vascepa/Amarin website:

"POTENTIAL MECHANISMS OF ACTION

Mechanisms responsible for the benefit shown in REDUCE-IT were not included in the study design. Potential mechanisms discussed, include TG reduction, anti‑thrombotic effects, antiplatelet or anticoagulant effects, membrane-stabilizing effects, effects on stabilization and/or regression of coronary plaque and inflammation reduction. More study is needed to determine to what extent, if any, these effects or others may be responsible for the CV risk reduction benefit demonstrated with use of VASCEPA in REDUCE-IT."