Torsten Ruger started this on 10.04.2014 after having read the Blue Book 20 years earlier. The main ideas were:

Mikrokernel: The microkernel idea: anything that can be left out, should, puts a nice upper limit on things and at the same time provides a great cooking pot for everyone else to try out their ideas.
Given gems and bundler this also seems an obvious choice. I really hope to see things i hadn't even thought of.
Layers represent an interface, not an implementation: It is said that every problem in computing can be solved by adding anohter layer of indirection. And so we have many layers, which, when done right, help us to understand the system. (Read, layers are for us, not the computer) But implementing each layer comes with added cost, often unneccessary. Layers can and should be collapsed in the implementation. Inlining, is a good example of this.
Empowerment: I like the openness of ruby. Everyone can do what and how they want. And change other peoples code in an easy and sensible way. The best ideas survive and even better ones are coming. Friendly competition as it were, cooperation, independant improvement all make ruby gems better all the time.
But ruby itself has not benefited from this in the same way (ie by ruby developers), because it is not in ruby.
To get it done: I don't know why this has not been done before, it seems so obvious. The Blue Book influence has left me interested in virtual machines and that hasn't gone away for so long. So when i bought my raspberry pi and had a real need for speed, the previous ecommerce project left me feeling that anything could be done. And so i started.

Thanks

This would not have happened without:

Smalltalk

Smalltalk is the mother of OO for me. Adele Goldberg has written down the details of early implementations in the Blue Book, which made a great impression on me. Having read it, mri code is quite easy to understand.
Unfortunately Smalltalk was too far ahead of it's time and used the image, the implications of which are still not understood imho.
Additional bad luck struck when, in Steven Jobs great heist of the PARC UI, he did not recognise the value of it's implementation language and so pure OO did not get the same boost as the gui. Instead we got difficult c dialects.

Ruby and Rails

After years of coding Java, Ruby was a very fresh wind. Smalltalk reborn without the funny syntax or image. Instead of the image we now have gems, git and bundler, so code exchange has never been easier.

Rails has sort of given Ruby it's purpose and made it grow from a perl like scripting language to a server programming environment with all the whistles and bells. Rails maturity and code quality make it not only a joy to use, but an excellent source for good ruby practises.

Synthesis

Synthesis is a microkernel OS written in the 80's by Alexia Massalin which not only proves the validity of the microkernel idea, but also introduces self modufying code into, of all places, the OS.

Alexia has raised questions about the nature of code and ways of programming which are still unresolved. I regularly reread the thesis and especially the chapter on Quajects in the endeavour to understand what they are in any higher language terms.

Many other steps on the way that have left their mark:

Judy has been a major source of inspiration and opened new ways of thinking about data structures and indeed coding. It has been the basis of two databases i wrote and together with Synthesis redefined the meaning of speed for me.

Metasm finally confirmed what i had suspected for a while. Namely that you don't need C to generate machine code. Metasm has be been assmbling, deassembling and compiling for several cpu's since 2007, in 100% ruby. A great feat, and the only reason i don't use it is because it is too big (for me to understand).

As ended up being the starting point for the assembly layer. It was nice and small and produced working ARM code, which is what i wanted, as raspberry is arm. Wilson got assimilated for similar reasons, ie small and no dependencies.

Parslet is great, thanks Kasper! Parslet makes parsing possible for everyone.

Bundler just makes you wonder how we managed before. Thanks to Yahuda, also for merb, which is not forgotten, and thor.