We're still figuring it out but I do recommend this detailed piece based on the certified vote results by county in the Philadelphia Inquirer. With all the caveats about interpreting county-level results it is striking the extent to which Biden received positive margin shifts across the state, including in many heavily white working class areas. The only exceptions were in a handful of rural counties and, interestingly, in Philadelphia. The biggest chart in the article (part of which is reproduced below) shows the change in two-party vote share for Trump for every PA county. Since it's two-party data you can derive the two-party margin shift by simply doubling the Trump share shift. The wide distribution of gains is quite apparent--and it all added up to a Biden victory.