change the bash output with stream editing

Question

If I call bash like this: bash|sed 's/a/b/g' every time bash outputs an 'a' it is replaced with a 'b'

$ bash|sed 's/a/b/g'
$ echo aaa
bbb
$ exit

However if I add additional substitutions like so:

bash|sed 's/a/b/g'|sed 's/c/d/g'` 

any output only appears after I leave the bash call:

$ bash|sed 's/a/b/g'|sed 's/c/d/g'
$ echo a
$ echo c
$ exit
b
d

Is there a way to have the case with two pipes behave like the one with one pipe? Or is there a way to do multiple stream substitutions in one call? Also why is it behaving differently in the first place?

Why would anyone do this?

I wanted to write a bash call, that would automatically redact ip-addresses like so:

bash|sed -r 's/([0-9]{1,3}\.){3}[0-9]{1,3}(\/[0-9]{1,2})?/███.███.███.███/g'

and it works great, but if I want to do additional substitutions, for instance for ip-v6, then it no longer works.

This is what I tried

bash|sed -r 's/([0-9]{1,3}\.){3}[0-9]{1,3}(\/[0-9]{1,2})?/███.███.███.███/g' | sed -r 's/([0-9a-f]{0,4}:){5,7}[0-9a-f]{0,4}(\/[0-9]{1,2})?/████:████:████:████:████:████:████:████:████/g'