Coach impedes his runner - out

[ozzy6900]

I am totally confused:

Huebner was focused on the plate. Gesell, well out of the coaches' box, was locked in on the other two runners on base and stepped into Huebner's path. Huebner bowled over Gesell and fell to the Whataburger Field turf. Huebner got up and scrambled home with the apparent tying run as the relay throw went past the catcher.

So, the 3rd base coach got tangled with his runner and they both go down. The runner gets up and makes it to the plate as the relay to F2 is overthrown.

If I have this right, where is there either interference or obstruction? If they both went down and the coach did nothing to assist the runner getting up, how can there be interference? It doesn't seem that the throw was interfered with in any way and no defensive player prevented the runner from advancing, so why was this not ruled a collision?

Please someone explain what the hell went on here!!!!