Not sure why transactions did not go through right away. I sent a transaction right on 16:00GMT but the amount never left the wallet. I think it was the third try before a transaction went through by that time is was 16:13GMT. Weird.
I think there were more transactions in a block than ETH can handle.
Increasing gas may have helped to get a higher priority, but not sure if that makes a difference.
Also many people forgot to increase the gas limit causing the transaction to fail.