He was offered a new contract to stay in Somerset, but cited Southend's ambition as the main reason behind his move.
"I had a couple of offers elsewhere from Yeovil and Crewe, but I've come here as they have great plans to move forward," he said.
"There seems to be a lack of ambition at Yeovil. I had to weigh up whether the club's going to make a push for promotion next season but maybe it's gone as far as it can.
"I don't think people are prepared to step out of their comfort zone to take a few risks to get out of the division.
"I don't think some people were prepared to back the manager at Yeovil as much as they could have done."