Did you read Ex. 29:4, cf. Ex.19:5,6; Isa. 61:6, and Mattl.3:1-6)? It was given to a nation who become a kingdom of priests. Water baptism was part of that covenant, to become a priest. The Gospel of the Kingdom is about Israel becoming that kingdom of priests. Of COURSE they would be baptized with water. It was a command of the Davidic Covenant. As long as God was dealing with Israel as a nation in Acts, it was done as to not offend the Jews.
Not when it was done to the Gentiles. Paul had Timothy circumcised because Timothy was of Jewish origin having a Jewish mother. That’s where the “not to offend” comes from. It’s clear that if any Gentiles thought to be circumcised it was seen as “going back under the law”. Not so with Timothy.