Tax exemptions are given to all religions that ask for them. Large monuments are not.
The same for everyone doesn't violate the anti-establishment clause.
Establishment of religion is to give preferential treatment to one religion over the rest.
Giving sponsorship to symbolic representations of religious ideas or to religious texts in monument format for one religion but not for all is establishment of the sponsored religion.
So: either everyone gets monuments, all together so as to be without favoritism, or no one does. It's that simple.
"No one does" is less expensive.