Terror of Mechagodzilla (1975) is part of the Godzilla series that is concerned with the spacemen, although I’ve apparently missed Godzilla vs. Mechagodzilla (1974). Given the era of the movie and its difficult to understand plot, it might be best to view this movie, no pun intended, through the lens of avant garde art. The close observer will see results before causation, extreme misanthropy, a disregard for reality in the course of events, the irretrievable transformation of humans to the ‘other’, and perhaps other sign that can be understood to be part of an avant garde attempt at monster movie making.
Or you can just call it bad movie-making and move on with your life.