I didn't say nobody would know of them. Just that they could be not known publicly. The rest is just tv stuff. The movies have shown they don't care and crossovers have only been a one way street so far.
Plus it's not like the movies have conveyed every aspect of the mcu. There are always new aspects of it to be explored.
Then you run into problem that they weren't in Hydra's radar per TWS, they were absent during the Sokovia Accords, SHIELD and Hydra have never recruited them, Hydra didn't experiment on them like the Inhumans, they were absent during several world - ending events, and several other items in the MCU that should have brought them up. The Inhumans explosion and round up being a big one.
If they drop the "it's all connected" mantra, they're in a better situation, but it's awkward either way.
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