Well there ya' go. He looked like he was running in sand because his first step off the base was just not worth a darn.
Your first move off the bag has be like a fast acting muscle action, not a long acting muscle action. It has to be bang and your gone. If that does not happen, you are trying to gain momentum long after you should have and the result is that you look like you are running in sand. I have seen him move, so I don't think the snap is completely gone out of his legs. I think he saw Bellinger set up, realized Bellinger was not that far out in CF and was setting up to have momentum going toward home for the throw and just let doubt enter his mind that he would not be sent. Then when he was sent, the opportunity to snap off the base was gone and he pushed off the base instead. He never made up the lost momentum. If you can watch it looking for that, see if you think he snaps off the base or pushes off the base.
To snap off the base your body has to be moving toward home before you leave the bag. You don't lean toward home and then wait to go. You get your body weight shifting toward home. Its an issue of timing. If your weight is not shifting toward home you end up pushing off the base instead of snapping off the base. If you are really fast, you might make up the momentum you lost. If not, you just look like you are running in sand and is that not what Kinsler looked like he was doing.
The problem with snapping off the base is that if you get the stop sign, you have to be able to stop without falling on your ass. That first snap step provides tremendous momentum toward home. Have to be able stop on a dime without falling over.
Before I forget, you are never looking for a go sign for the tag up to go home. You assume you are going without doubt and are only looking for a stop sign as you start home.