Well, Miller created Max, which back in those days was more about composition than synthesis and relied on external hardware to create sound. Another fella took Max and developed the commercial product and developed it some more. During this time home computers became good enough for realtime synthesis so Miller developed PD which combined aspects of Max with realtime audio synthesis capabilities. Max thought this was pretty great so integrated pd into Max which gave us Max/MSP, Max is Max Mathews who developed the Music(n) family of programing languages and MSP is Miller S. Puckette.

I would not say that pd or Max/MSP is more approachable, they are pretty even these days unless you stick to vanilla pd with no externals which almost no one does, the main differences is that Max/MSP gives you all you need out of the box but pd can run just about anywhere including in plugins if you are that sort. Max/MSP is considerably more modern in aesthetic but PlugData[0] and PurrData[1] offer more modern interfaces for pd with a few new tricks, PlugData is a plugin version of pd (also standalone), Purrdata is a JavaScript rewrite of the interface with prepackaged externals and solid documentation. And we have a handful of other varieties of pd each which have their own slant and can be found on puredata.info.

0: https://plugdata.org 1: https://www.purrdata.net

Edit, ok not having a dozen different varieties and hundreds of externals to choose from does make Max/MSP more approachable. I was mostly speaking from the standpoint of use but I realized all I did was say that pd is an example of a major flaw of OSS in the days of analysis paralysis.