I’ve never tried to do what you have, but you aren’t going to achieve your goal using Blynk.begin.
You need to use Blynk.config and Blynk.connect instead.
It might be worth you reading this, and the included link about using Ethernet and WiFi at the same time, or as a fallover…
This isn’t going to give you a ready-made solution for your hardware (or for the LILLYGO board either) but might point you in the right direction.