Looks like Assange was attempting to destabilize Ecuador's govt while in the embassy (at least that's what they claim).

“Ecuador’s Interior Minister María Paula Romo says Julian Assange's asylum was revoked because there was sufficient evidence that he was meddling in Ecuador's internal affairs in an effort to destabilize the government.

Romo also reiterated President Lenin Moreno's remarks that Assange was consistently violating embassy residency rules, and specifically called out how he would put feces on the walls.”