I haven’t read von Däniken in a number of years so I can’t really go back now and say whether or not there was anything specifically racist in any of his beliefs or assumptions, but I think the case can easily be made that he had a sort of techno-centric arrogance which assumed that primitive peoples couldn’t possible have built the great monuments that they did because we can’t figure out how they did it. (Or are unaware of the fact that somebody has, but it’s not well publicised.)
It’s an assumption which ignores the fact that humans are problem solvers. If there’s a way it can possibly be done, even with brute force, muscle power, and simple tools, somebody can and will find a way to make it happen. Brain power is brain power, and just because we don’t know or understand how somebody could achieve something doesn’t mean that somebody else couldn’t. To suggest otherwise is no more then an appeal to ignorance.