question about eren at the ending

my theory is that eren is able to control the founding titan without the need of zeke because eren woke ymir up to stop just following king fritz. but then the rumbling stopped as soon as zeke died but I just think eren made it seem like you need a royal blood to control the founding titan so that when they are able to defeat eren and make them look like a hero.

and also was eren controlling halucigenia or did it have its own will and turned the eldians into titans