In “Ultraman,” for example, there were several episodes in which multiple monsters appear.
But in all these episodes, only the single strongest monster had a bout with Ultraman, having the rest of them beaten by SSSP or in internal battles between monsters.
It should also have been difficult to have multiple monsters appear in one episode because it’s costly.
SFX TV series other than Ultra Series commonly had the same monsters appear throughout a few serial episodes or in different episodes at the time.
It’s worth admiration that Early Ultra Series provided us with a new monster every week basically.
I also interpret the one-on-one bouts as a sense of aesthetics the crew had in those days.
That helped to make the fighting scenes look gracious and also highlight the strength of the superhero.
Among boys like us it was well perceived that a one-on-one fight without having a weapon is a manly act.
Ultraman and Ultra Seven might have been heroes to embody the ideal as they wouldn’t have and use any particular weapons such as a sword or gun though they had light weapons. 🙂
I’m not denying the later Ultra Series, and it might be a matter of liking.
But it’s true l feel something like “beauty of form” in the one-on-one battles shown in Early Ultra Series.