My school focused on one "system" per block. Each system covered anatomy, physio, embryo, biochem, immuno, and the basic science portion of the system in M1. M2 went through all the systems again, reviewing previously learned material, plus adding pathophys, pharm, micro, and clinical medicine (aka how do you actually diagnose this and what tests/treatments do you order). Blocks lasted 3-5 weeks depending on the subject. We also took OMM, bioethics, and a "clinical medicine" course alongside whatever block we were on.
An easier example is that we covered all of biochem in the first 2.5 weeks of med school and all of immuno (in greater depth than 1 semester of UG) in 2 weeks. First day of biochem our professor put up a diagram and semi-jokingly said "By then end of this course you should be able to draw and understand this diagram from scratch." We all laughed a little and then he got completely serious and said "I'm not joking." At which point we all became instantly horrified. He wasn't joking. This was the diagram:
It sounds overwhelming but once you adapt it sort of becomes natural. I looked at my sister-in-law's syllabus for her UG genetics class she was complaing about and thought "lol, this seems so chill." but in UG I probably would have thought it was a pretty challenging class. The vast majority of the time it's not particularly hard info to learn, it's just a large volume and requires strong organizational skills and not just hard work. Once you get your study strategy down and get into a groove it's not as insane as it initially sounds.