‘To the weak became I as weak that I might gain the weak. I am made all things to all men’, that is, I bear in mind their understanding and their reasoning, and their use of language, and I carefully tailor my approach to what will be helpful and effective to them.
He adapted to their vocabulary. Maybe he gave shorter addresses, particularly if there were lots of children, used plain terms. Some preachers will even preach the gospel in three and four syllable theological terms, which outsiders and unchurched people would never understand. To the uneducated or the uninformed you adapt. For children you use many more illustrations, and you are never aggressive in presentation or style. That will of alarm them. That is what the apostle means: ‘to the weak became I as weak, that I might gain the weak. I am made all things to all men.’ It is to do with the presentation of the message, not the adoption of lifestyle.