Can A View Load All Data, And Filter (Hide) With CSS? When using an exposed filter in a view, any data that doesn't meet the filter is removed from the page. Partially for SEO reasons, I'd like all the data to load (and stay in the HTML), but then the exposed filters will simply use CSS to hide the data that doesn't match the filter.

Does that make sense? Is it possible?
A module might be able to help you with this
https://drupal.org/project/mixitup_views (drupal 7 + 8)
Loads all items and might be close to what you need
https://www.drupal.org/project/isotope (drupal 7 + 8) A highly customizable module that is probably harder to implement as well
Some other alternative modules
https://www.drupal.org/project/views_semantic_tabs (drupal 8) might be a good fit
https://drupal.org/project/shuffle (drupal 8)
Not sure if it loads all results at once but it offers the filtering you described
https://drupal.org/project/views_quicksand (drupal 7)
does not load all results at once by has the filtering effect that you need so it might be a starting point
NOTE: all or almost all above module use JS libraries that you have to pay for if you implement them in commercial products
A custom alternative
Create a view that displays all results
and use global text area to rewrite all the elements to be part of a container div
and add classes to the container based on the categories you want filterable
Then use this code https://codepen.io/terf/post/jquery-filter-divs
in your custom module or theme changing box class with your container's class name