少し前のことになるが、私は或る評論家がインターネットのウェブサイト上に。。。
Generally, when I see ことになる, it means something along the lines of "it is/was decided". But here, that meaning doesn't seem to apply. What is the nuance being communicated here (if it helps, this is the first sentence of an essay)? Why not use 少し前のことですが ?
Here it isn't really ことになる as a set phrase, but [...こと]になる; i.e. you can substitute the first part from something else and still maintain the meaning here.
長い話になるが、
As for the "why not ですが", IMO using なる feels more like "it's gonna end up being" instead of just "is": This story I'm about to tell you is going to end up being about something that happened some time ago, but... humour me...
