It was _kind of_ a historical accident, in the sense that if we ran history over again, it wouldn't be too surprising to see an alternate-history "Conway's Life" with a rule like "B36/S23" (HighLife) instead of "B3/S23". (Conway did really like the replicator and bomber and a few other fun things that HighLife has that Life doesn't.)

On the other hand, Conway had some very specific criteria for the rule he was looking for. "B3/S23" is about as simple a set of rules as you can find for a range-1 Moore-neighborhood outer totalistic cellular automaton on a square grid.

So unless Conway's eye had happened to get caught by some slightly more complicated rule before he and his team happened on B3/S23, he'd be quite likely to settle on "B3/S23" all over again. It's one of the few candidates for the simplest rule that does obviously interesting things and seems likely to allow for computational universality. I mean, there are untold numbers of equally promising rules in larger rulespaces like the "isotropic non-totalistic" rules

  https://conwaylife.com/wiki/Isotropic_non-totalistic_rule

... but most of those have rulestrings like "B2ci3ai4c8/S02ae3eijkq4iz5ar6i7e": it's just not anywhere near as simple to describe the rules, as it is for Life.

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If we meet up with an alien civilization some day, it would be extremely amusing if we happened to show them some Life patterns and they said (in so many words) "Hey! You know about Pnurflpeef's Game of Life?!?" Not a likely scenario, by any means, but not quite impossible either.