Divide glorious into syllables: glo-ri-ous
Why is it glo-ri-ous and not glor-i-ous? And shouldn’t "glo" be pronounced as glow?
Which syllable division rule is used here?
The syllabifications from Merriam-Webster, which it seems like the program you link to uses, were settled upon over 100 years ago and most of them haven’t been updated when the pronunciations changed.
In English, a syllable is generally not hyphenated after a vowel if it’s a lax vowel or an r-influenced vowel.
Why are coral and floral hyphenated cor·al and flo·ral? Because in the 19th century, these words were pronounced1 core-al and floe-ral, as you can see by looking at the 1892 Webster’s High School Dictionary (linked to from those words). Today, Americans no longer distinguish the vowels [o] and [ɔ] before an /r/, and Merriam-Webster’s pronunciation shows that coral and floral rhyme.
In the 19th century, as you can see from that dictionary, glorious was pronounced with the vowel of floral, and not of coral. So it was hyphenated after the o.
1 at least by the people who Webster thought mattered.