That’s because your PassThrough is waiting on the first Excel node, not the python node. The passThrough input is what gets passed on and the waitFor input is what’s waiting to be execute before moving on. You don’t need a PassThrough or Wait node if the node you’re waiting on is also being passed on to the node you want to wait. A node has to have an input to execute (that’s how Wait nodes work) so you can typically rely on a node not executing until the node connecting into it has finished.
Also, as an FYI, please paste code as preformatted text from the source. Your second post is still unformatted since (I’m assuming) you copied it from the original paste, which is unformatted.