It’s impossible to say what someone was thinking. You can’t get inside their heads and examine subjective feelings which led to the act. All you can do is talk of historical context.

It’s worth saying that sati was incredibly rare, even before the Brits arrived. There are prior Mughal proscriptions against the act, but they indicate it was an isolated and regional problem, mostly confined to Rajputana during Mughal rule. It was different during British rule, when it seems to have predominantly involved Bengal. There’s some reason to believe that at least some of the Mughal stories confuse sati with jauhar, which was a different but related practice.

In its original meaning, “sati” says nothing about self-immolation, it simply means “pure” or “chaste”. In the Manusmriti (around 200 BC), sati is not an action, it’s a person – a woman devoted to her husband. There’s no mention of burning. The oldest mention of sati in Hindu literature comes from the Mahabharata. Prince Yudhishthira asks the sage Markandeya if he’s ever heard of a woman more devoted to her husband than the princess Draupadi, and Markandeya relates the story of the sati Savitri.

Savitri is a woman who falls in love with and chooses to marry a man named Satyavan, despite knowing there’s a prophecy that Satyavan will die a year after his marriage. The story is about how she talks Lord Yama, the god of death, into sparing the life of her husband. There’s no burning involved, no sacrifices. Yama is awed by her devotion and spares the life of Satyavan, and the two live happily ever after, as fairy tales go.

There are literally dozens of women in Hindu literature honored as sati, who didn’t jump into the funeral pyre with their husbands. If you ever attend the Hindu festival of Karva Chauth, you can hear women today reciting ancient stories of hallowed women from the past, satis who drew the respect and favor of gods, but didn’t actually burn themselves.

It's hard to figure when sati acquired its secondary meaning of self-immolation on the funeral pyre of the husband. There are sati stones and sati temples dating back to around the 6th century that commemorate women as sati but it's not clear whether they're talking about a woman who burned herself to death, or simply a woman who was recognized for being an exemplary wife.

The earliest unambiguous historical accounts we have of ritual suicide by fire come from 12th century Rajputana, via Islamic literature. But these aren’t actually sati, they are cases of jauhar.

These were cruel times, and in warfare no mercy was shown to the defeated. Women on the losing side faced the prospect of rape and torture in the hands of the enemy. Rajputana had a very martial culture, honed over centuries of warfare with the Muslims. They evolved a custom of ritual suicide.

If their town or fort was besieged by superior numbers and there was no hope of victory or escape, they would commit suicide. Men performed a puja (religious ceremony), then marched out one last time to die in battle. Women built a big fire in the center of town and walked into it. This was jauhar.

The difference from sati is that these women weren’t walking into the pyre of their husbands - the husbands were outside fighting to the death against the invaders. They were doing it to avoid rape and torture and death at the hands of the enemy. They picked a rather painful way to die to show that they weren’t taking the easy way out; it was for honor and not out of cowardice.

The story from Bengal is different; there are indeed reports of women climbing into the funeral pyre after the deaths of their husbands. Almost all of these reports are confined to upper caste women, the elite of society. These reports come from legal investigations by the Brits.

When the East India Company took over the administration of Bengal after the Battle of Plassey in 1757, they legalized sati, provided it was voluntary. As such, they were obligated to investigate each case of sati to ensure it was voluntary. And they kept records, at least a dozen cases between 1757 and 1829, when it was banned by Lord William Bentinck. None of the cases was determined to be illegal.

Under pressure from Hindu reformers such as Ram Mohan Roy and from British missionaries, the EIC finally banned the practice in 1829. However, sporadic cases continued, and still do to this day. The last reported case was as recent as 1987.

All cases are investigated, but it’s hard because it happens in remote places with poor law enforcement. And also because the climate dictates that Hindus cremate early, within 24 hours of death, so any sati cases are always reported after the fact when the woman is already dead and can’t be questioned.

Since the number of cases is so extremely low, it’s not possible to do statistics. It seems fair to say that at least some must be cases of forced sati where the woman was persuaded to kill herself. Probably the reason is over inheritance – if she kills herself, someone else inherits. That’s government policy, anyway – they start by asking who benefits from her death.

But there are certainly cases of voluntary sati, cases where the widow had to be physically restrained to keep her from jumping into the fire. And cases where she managed to break free and kill herself. In my opinion, that amounts to mental illness brought upon by extreme stress. I don’t know if we can analyze it any further. Desperate and sad people do desperate and sad things. It’s incredibly rare, but it happens.