Yes, Trafalgar was a turning point for Spain.
In my opinion there are some key points:
- Mistrust: after what happened in Cape Saint Vincent, the Spanish didn't trust in the French, so Napoleon ordered that the ships were mixed (2 french and 1 spanish in the middle). There were tensions between them and that didn't help.
-Way of shoot: the british always shot at the hull in order to inflict as much damage and casualties as they could, but the spanish and french usually shot at sails in order to dismantle the ship and capture her. That's one of the reasons of why they had less than 500 dead.
-Crews: while the british were always at see and well trained and motivated, the allied crews were in harbour (even for years), and some of them had never been on a ship before. That means you have no experience, no training, and no faith in what you are doing. Some of them were forced to serve in the navy, even prisoners, in order to fill the crews needed to sail a ship. When the battle started, some would use a gun for the first time, so the accuracy they could get was not comparable to the british. They fought the best they could, considering the circumstances.
-Superiority: as a result of breaking the allied line, there was a continuous superiority in ship numbers.We know that in some cases they had to fight against even 7 enemy ships at once, so you can guess the result.
We know as well that some ships at the vanguard of the line kept on sailing getting away of the combat (Dumanoir was the commander there and he didn't obey the orders given from the Boucentaure.... some say that he didn't see the signals)
Before the combat took place, Gravina (Spanish commander of the rearguard) asked Villenueve to give him permission to act separately and the french answered negatively.
So, the bloody combat was just in the middle of the allied line and the british ships were coming to join the party while the vanguard did nothing. Well, eventually some ships decided on their own to disobey orders and turned into the battle, but it was too late.
For instance, we know what happened to the San Juan Nepomuceno, commanded by Churruca, which had to fight 7 ships. He ordered to nail the flag because he didn't want his ship to be captured.
- Villeneuve's order to tack the line towards Cadiz: this is in my humble opinion, the worst decision he could have taken. Different types of ships, they didn't sail the same way, literally it resulted in a chaos leaving the british the room they needed to brake the line. When Villeneuve gave this order, many of the Spanish officers said that the fleet was doomed and that he didn't know his proffesion. We will never know what would have happened if he hadn't given that order.
- The decision of leaving port itself: the allied fleet was safe at port, and they knew that bad weather was coming, so the british would have to deal with that at sea damaging their ships. We all know that a big storm ocurred after the battle, sinking some of the ships that had received the worst part of the battle. If they had decided to leave port after the storm......well, we will never know.
I could write more about this, but as a summary those are important points to me.
I would be pleased if you have more ideas and want to discuss them here.