It says in the Kitzur Shulchan Aruch (104:2), "One who disgraces Chol Hamo'ed, even though he has to his credit Torah and good deeds, has no share in the World to Come." Disgracing Chol Hamoed implies not honoring it with... wearing better clothes. Therefore, every man is obligated to honor it... and to wear dignified clothing."
1) Why does one lose his share in the World to Come just because he disgraced Chol Hamo'ed?
2) What does wearing better clothes mean?