I believe the necessity for retreat in enlightened beings is because it is very easy to be swayed by the surface opinions of others and the demands of normal life when living in society. Isolation helps us investigate what is in our own heart (and I believe any ultimate truths must reflect what is within our fundamental self) - however all these people then applied what they had discovered about their own self in the real world.
Is aikido a path to enlightenment? There are many muslims, buddhists, christians, hindus etc who are very knowledgeable about their faith and practice it devoutly - however they may not be enlightened because they don't actually feel it with their 'bones'. Also, talking philosophy and acting is different. Someone has this as a quote at the end of their messages; 'don't argue about how to be a good man, just be a good man.' (Marcus Aurelius).
Aikido lead me into eastern thought, which has fundamentally changed the way I view myself and the reality. However it needn't necessarily have been like that. One thing, however, that aikido does do (and most are not aware of until it happens) is that it trains us to have a non-negative attitude to aggression and to produce a non-lethal (and often non-harmful) response to an attack.
I think enlightenment can be gained from anything (as in the various zen stories) - it just requires seeing into the very nature of reality and that requires an internal process which cannot be forced from outside.
P.S. I'd agree with Lynn and George about reality being beyond words and normal conception. However I beleive, enlightened people show similar behaviour. Whereas in christianity goodness leads to heaven/god. I believe goodness eminates from enlightenment/god/whatever you want to call it. i.e. if you are enlightened you do the correct thing because you understand the nature of reality - you don't do good things just because someone has told you they are good and that will make you more holy.