Well, if you've ever been to Berks, it's not hard to see, lol. It's also just more of a 'rural' suburban area compared to Montco and Chester.
Montco/Chester, and Bucks to an extent also seem to get a lot of college+ people moving in, while Berks is not seen that way (as the first choice for the "suburban" outside Philly life, obv)
Why is Bucks so much more republican than Chester, Delaware, and Montgomery counties?
Bucks, while fairly well educated, is a bit more WWC than the other three. It is also only recently that Bucks has become more Republican than Chester. Granted it was by just a few hundred votes, but Romney actually won Chester in 2012. Chester has trended heavily Democratic since then due to the GOP's problems with the college educated vote under Trump. As VPH pointed out Bucks has a few trends that cancel each other out and as a whole has been stagnant.
