If it's obvious to anyone with a telescope, that at least Jupiter is a sphere, why would Earth be flat?
One answer I hear from flat earthers is that other planets are round, but not Earth.
The other answer is that space is some sort of projection, and you're not seeing planets are all.
How does one understand something without questioning it?
If your goal is to understand it, the questions will be illuminating. If your goal is to dismiss it, your questions will be cursory