In this shiur we unpacked the classic machloket between Tosafot and Rambam as to when Hannukah candles must be lit. The Rambam reads the gemara as requiring one to light within half an hour of sunset. Tosafot understands that, because we light inside, one may light later. This change in the practice of lighting had an enourmous impact in the halakhot relating to Hannukah candles. We will continue to encounter this as a reason for shifting some specific practice.
You can find the mekorot for this shiur at this link.
Here is the audio of the shiur: