I don’t think we need the GAFAM to leave to obtain this situation, strong and meaningful regulation (like the DMA) should be enough to make room for sane competition.
Also, the EU is really smart here because they are not doing protectionism. So if GAFAM decides to leave, they’ll take the risk of new competitors which would have no reason to be banned from the US market.
As soon as Apple/Meta/Google/... sulk and leave, other companies would find the space to grow and fill that space with similar products which would respect the users.
Users outside of Europe would realise it's possible to have those kinds of products without abusive practices, and would start demanding Apple/Meta/Google/... for the same.