He just announced this himself on his website. Rodrigo started managing the team in 2016.
Pessoa's target with the team was the qualification for the 2020 Olympic Games, a goal he met. During their road to this qualification, they picked up a European title, one they've been waiting for fifteen years for.
During his reign as manager, he collaborated with more than 30 Irish riders, and, he says "is proud to have worked with them during my tenure."
Pessoa will now turn his attention to his family, his business and his own riding.
Whom his succesor will be, is not known yet.
Source: Website Pessoa