After starting the series with a 3.2% chance to win according to ESPN, they have raised the Heats odds to 35% after taking a 2-0 lead. According to said model Celtics still have a 47% chance of winning the title.

Link here https://www.espn.com/nba/bpi/_/view/playoffs

This is the said model that everyone keeps quoting 3% based on. It gave the heat 13% odds after winning game 1. For comparison 538 now gives the Heat a 70% chance.