The idiomatic expression "to see happen" means to witness or experience something firsthand. It can also imply that one is actively involved in bringing about a particular outcome, either by their actions or decisions.
Sentences with «to see happen»
I think it would take a lot of work and coding to add it so I don't see it happening in the near future, but it's a cool suggestion! (emilybites.com)
You wouldn't see this happen at any other big club, so why should we have to put up with it? (justarsenal.com)
I have seen this happen all too often in the short decade I have worked in education. (hechingerreport.org)