I don't think there really is any excuse that can be given for those that choose to not be better people and go on to treat people like they are bigger every time they do it. There is simply no sense in attempting to demean others, unless it is that you yourself are actually quite small on the inside.
Like the saying, "hurt people hurt people," it is actually those that aren't whole within themselves that seek to drag people into their mess so as to give themselves some form of validation for their puny self-worth.
It's okay to admire other people, and maybe even wish to be like them. But taking it to a whole other level by being jealous and then seeking their downfall is just gruesome.
You're completely correct, usually this behaviour stems from a distinct lack within a person; a lack of one or many things they cannot find the courage to address themselves..so they try to read others down to improve their feeling of self-worth all the while loathing themselves and inhibiting any potential gain that could make by applying negativity to their own life instead of positivity.
The best way to improve self esteem is to improve someone else's but people like I mention in this post have an inability to find the ownership for such things and so their lives remain small and insignificant.