Two points: 1. most guns don't have safeties, and 2. safeties are pretty easy to toggle

First, many guns don't have any sort of safety like you see in the movies - "toggle this button to make the gun able to fire." Most safety features in current guns are to prevent the gun from going of accidentally - i.e. other than someone pulling the trigger. Therefore, the most common safeties are a trigger dongle and a firing pin block, which makes the gun drop-safe. In other words, if you drop the gun, it won't go off, but if you pull the trigger, it will go bang. A Glock is a prototypical example of a gun with no safeties - most police departments in the US issue Glocks to their officers, and if used correctly (i.e. keeping your finger off the trigger), they are thought to be very safe (as far as guns go).

That said, for guns that do have safeties, safeties are generally very easy to toggle on and off. A 1911 style pistol is fairly common and has several safeties. 1911s have both a grip safety and a safety on the frame. If the gun is on safe, the safety is "up", and when you grab it, you release the grip safety, and your thumb should sweep down and release the frame safety. Many people "ride" the frame safety, which means they just keep their thumb on the safety since it's a comfortable ledge. Once you're done firing, you should sweep your thumb up to put the gun back on safe. Both safeties are intended for the same purpose as Glocks - to prevent the gun from firing when you don't intend it to (like, into your leg when carried in a holster). They are not intended to make the gun an inert object.

Many new gun owners want a safety because they think it's an added layer of protection against you doing something dumb. And it is, to an extent, but once you become more familiar with safe gun handling, a safety is basically extraneous - it generally won't help from anything catastrophic (like what happened in this article), and is a potential point of failure (for example, there are stories about marines with berettas having them go from safe to unsafe because of plane vibrations). Once an owner trains to become proficient with their pistol, having a safety or not is basically a wash - doesn't matter either way, as long as you're handling the gun properly.

With all that said, that means any pistol that is not secured by a lock or case is 100% unsafe to be left around children, safety or not. There are plenty of "quick access" safes that people can install in their cars that will allow a pistol to be secured, but also retrieved quickly. Having a totally unsecured firearm is simply negligence.

The handgun does not necessarily have a safety. Also, many people will keep a round loaded in the chamber so that they can respond to threats as quickly as possible. Draw and pull the trigger. Leaving the gun in your car probably doesn't fit in with this strategy, though. I think mixing these circumstances with a toddler is pretty fucking stupid.

The strength required to pull the trigger will depend on what kind of gun it is, and how they've configured it with the springs inside. A double action revolver will usually require lot more force and travel than a semi automatic pistol.

Best guess, without reading the article, is that the gun was the in-car gun or the carry gun left in the car. It was likely loaded with one in the chamber and no safety or safety off while carried (so you can shoot people faster.....for all those gunfights you get into). I CC and will definitely unsafe my gun when walking at night or in a shady area...but otherwise it is buttoned up and safed.

Or they bought it so their toddler can shoot himself easier with their gun.