I remember something about the nobles blocking a match with an aristocrat, so maybe Catherine said to heck with them, I’ll just marry for love.
Probably. She was a pawn in a very complex game. Deciding to blow off the whole thing (or close your eyes and roll the dice) has a lot of win percentage, if there are no obvious good choices.
For comparison, we could look at Henry VIII’s surviving wives, Anne of Cleves and Katherine Parr. Anne was divorced and settled with a pension and a comfortable place at court as “the King’s beloved Sister.” Katherine, his widow, married again but died giving birth.