Your assertion that understanding climate change in the 50s implies a natural cause is simply false.
Take from that what you want.
>then what we have done since should be way more observable without advanced tools and research. But it's not.
This is also asserted without evidence.
Around 1950 the global emissions of co2 from human causes was about 5 billion tons. It explodes after 1950, hockey stick like growth and is now about 35 billion tons.
Humans have produced more co2 in 70 years than we have since we started to walk on two feet.
Take something like general relativity for example, which was first theorized in 1915 and predicts things that we're only validating today. It's completely possible to predict something before it happens by understanding the underlying mechanisms of its action.