According to Eliza, why did Darcy separate Jane and Bingley?

Elizabeth was correct, however, in her belief that Darcy had played a big role in preventing Bingley from proposing to Jane. However, Elizabeth's partiality for her sister blinded her to the fact that Jane, with her always calm and cheerful disposition, really did nothing to demonstrate her particular affection for Bingley. Elizabeth had assumed that Darcy's actions were only the result of his class consciousness, but never considered that Darcy may have simply wanted to prevent his friend from the pain of rejection.