Page with Category Returning 1

few things here:

1) Your WP_Query args doesn’t look good, the proper way of querying posts by taxonomy should be:

$splash_page_args = array(
    'post_type'      => 'page',
    'posts_per_page' => '3',
    'tax_query' => array(
         array(
             'taxonomy' => 'category',
             'field'    => 'slug',
             'terms'    => 'splash-homepage',
         ),
    ),
);

2) Is there any particular reason why you’re using foreach instead of standard WordPress loop? If you want to keep using the foreach loop, then your posts objects are not in $splash_pages variable, look for them in $splash_pages->posts.

However, I’d recommend using WordPress loop like so:

if ( $splash_pages->have_posts() ) :
    while ( $splash_pages->have_posts() ) : $splash_pages->the_post();
    ?>
        <h2><?php the_title(); ?></h2>
        <p><?php the_content(); ?></p>
    <?php
    endwhile;
endif;
wp_reset_postdata();