Oh! Planet Money just did a really good episode on this exact topic.

It’s complicated and I recommend a full listen to the episode, but the big two reasons are:

1. The cost of building out all the new infrastructure is partially paid for by the data centers, but the majority is paid by all customers.
2. The demand for electricity is growing much faster than supply can be built.

Those two, combined with the deregulation in most markets, has meant that the price for everyone is going up.