In a lot of ways.
One thing was his compositions. A lot of them are jazz standards and pretty popular ones at that.
Another thing was the fact that he could get such a great sound of a garbage horn and mouthpiece. He constantly sold his horn for heroin (unfortunately), and often played on stock pieces and beat-up horns.
The way he soloed was the most influential. I mean of course he could play in every key, but the way he played in every key was amazing. There were no "wrong" notes in his solos. He was one of the first to really experiment with playing notes that would traditionally be considered "wrong" in the key. Before Bird, it was almost unheard of to play the kinds of notes he did. The way he used these notes sounded excellent too- it was very lyrical and wasn't insanely dissonant and painful to listen to.
One of my favourite quotes which also sort of explains his influence is "Music is your own experience, your own thoughts, your wisdom. If you don't live it, it won't come out of your horn. They teach you there's a boundary line to music. But, man, there's no boundary line to art."
Studied Bird's music a lot