Remember that bunch grasses are climax species, not pioneers. They do not establish a site, they provide long term cover. Pioneer wildflowers will disappear in most communities after a few years. They've done their jobs and disappear until they are needed again. That is why in most plant communities you have to replant the wildflowers every few years.
Bunch grasses live for years.
They need their companion wildflowers to survive long term. Work for the long term not short term. It probably took years to mess the site up, expect to spend some time fixing it. It would be lovely if planting wildflowers or grasses would be all that is needed to restore a site to its native state. We have found an ecosystem cannot be easily restored if weeds are present.