The reason he became filled with pride was he looked around himself and said "Gee, look at all this material wealth I have. I must be pretty hot stuff or else I wouldn't have all this stuff. I am such hot stuff that I really oughta be in charge around here... well I just will be in charge around here. I'll be higher than the highest, I'll be even hotter hot stuff than I am right now already... watch this."
And then we know how that worked out for him. So technically, money isn't the root of all evil but the LOVE (Oh, I love it so much, it makes me such hot stuff to have so much of it) of money truly is the root of the original sin of pride, and thus of all evil.
Recommended reading: The book of Isaiah.