Why did the Capital build a stage and bleachers for Americans to Protest on J6?

Thom Tillis knows why

This is the capital steps on an average day

This is the Capital on January 5th, 2021

Temporary bleachers and a podium, with a media camera tower, were assembled, for Americans to protest the Congressional session, the next day. Why did the Congress build this platform, and then put a fence around it? Then arrest every American they could find, who walked inside that fence!!!!

Why?