The building is a symbol, as is the act of destroying it.

Symbols are given power by people. Alone a symbol is meaningless, but with enough people, blowing up a building can change the world.
Remember, remember!
    The fifth of November,
    The Gunpowder treason and plot;
    I know of no reason
    Why the Gunpowder treason
    Should ever be forgot!
https://t.me/qanonbelgium/26667