You almost always want to get a contract extended before it expires for multiple reasons.
1) Consistency. If you are making/receiving promises, you don't want those obligations to lapse. It's a bit of a pain to "turn off" your obligations and then "turn on" once an agreement is reached again, for lack of a better word. The parties also both benefit from sustained expense/income instead of it lapsing.
2) Timing. These things take a while to negotiate and you want to make sure you have plenty of time to work through any concerns so that you can keep things moving without a lapse in contract.
3) The worst one for Nick, retention. In his specific case Rumble would want to lock Nick down now. You don't want to lose talent to other offers, so the earlier you extend the contract the less chance you have of talent being poached. The fact that Rumble is seemingly unconcerned with this is very telling. Not a good sign for Nick.