I think he was mostly known for that unloved Halloween 6 movie but yes Clueless got him on the map.
It sucks he drew the short straw here and played the unlucky guy who Juliet is basically contracted to marry... Paul Rudd actually plays him as a decent guy but Juliet's dad is too aggressive about everything
Yeah Leo always looked too young for Titanic to me. Weirdly enough, he seemed more comfortable speaking Shakespearean dialogue than James Cameron's