Instead of thinking about thought processes and human frailties of logic and perception, the situational factors that lead to making decisions are worthy of some attention. In many cases, the situational factors, not any decision making process can drive the decision to make a decision.
The military principle of leadership is to "Lead, follow, or get the heck out of the way". The real challenge of leadership lies in making the right decision about leading, following or getting out of the way, and many a wrong or right choice has been made with historical results.
There might be urgency. One of the great sales tactics is to set a severe time limit for a discount or bargain. When a person would normally wait until there is cash or need, they might over spend or use credit in order to not miss a great deal.
In a crisis, perceptions have even more power to drive the decisions. Whatever it is that a person perceives will be the foundation of the decisions that they make. If there is a perception of danger or harm to another, there will be decisions to move away or to act. This is how people react to a screaming child or intervene with a couple that seems to be fighting. Others will have perceptions that the screaming child is just having a normal meltdown or that the couple is just engaging in horseplay and will move on.
If the perceptions are in error, then the decisions will be in error. Screaming children are kidnapped by strangers or the abusive half of a couple gets away with a public assault and no one steps in.
There might be knowledge or ignorance. In the absence of any other knowledge, a person might make a decision that is based on what they actually know. This leads to decisions to do something with skills that have never been learned or done before. Small children have helped to deliver their little brothers and sisters, rather than freezing or running off.
Plenty of people decide to invest in everything from small business enterprises or fixer homes, to crafts and hobbies on the "learn as you go" plan. The expectation is that, over time, following instructions, doing things, making mistakes and meeting challenges will eventually create a knowledge base.
Thus, the combination of need to do something on one's own and the expectation that knowledge will develop through action is one way that people decide to act.
Valuation is a consideration in decision making. There is the standard teaching of evaluating the alternatives and selecting the one that appears to be the best choice. Then there are some strange ideas that people have when evaluating risk, reward, benefits, prevention, reaction and so on.
One classic economic principle involves valuing future results more than we value present results. The old example of turning down and offer of double our money tomorrow for double our money a year from now comes from a tendency to value a future outcome more than we value a present outcome, even if both outcomes are the same. Strangely, it is not until a year later when we look back that we see far more value if we had taken the reward a year ago.
Past experience, knowledge and imagination can truly change the way that we make future decisions. Past trauma can cause a person to decide wrongly, rightly or to freeze and make no decision at all. Teachings and beliefs that are formally and informally derived will definitely affect decision making.
An environment of imagination and hypothetical thinking can lead to better decision making processes or can cause distorted, unreliable or erroneous conclusions about future outcomes, thus leading to bad decisions.
When the imaginary and hypothetical thoughts come from fear and negativity or from grandiose and unrealistic expectations, problematic decision making can occur. Then again, some of the greatest works of fiction and some very spectacular accomplishments have come from grandiose expectations or from fearful imaginings.
On the positive side, imagining or hypothesizing different outcomes can come from experience, from knowledge bases or from sound logical thinking, and can enhance decision making processes. Negatively, too much analysis and hypothesizing can lead to inaction when action is needed.
In summary, there are thousands of factors that will affect and even change an individual's decision making processes. Only a few of them have been discussed here. But these few factors do affect a lot of the decision making processes that people go through, especially when someone asks "What on Earth were you thinking about when you decided to do that?".