Can some brilliant MNer please explain to me how the fracking vote brought Liz Truss down?

Short version:

If govt declares their MPs must vote a certain way & the govt loses the vote, traditionally this means the govt has lost the support of the House of Commons, and that is same as govt falling apart ,lost a majority, general election is justified.

Long version

MPs in a party are told how to vote on specific bills.
The people who go around telling the MPs how to vote are fellow MPs, called the Whips.
if a party rejects an MP (for any reason) that MP is said to have "lost the Whip."
Losing Whip means losing party funding & support to run again for their seat in Parliament.
The Whips were told fracking vote was a "three line whip" vote. that means, if any Tory voted against govt, that MP would lose the Whip.
Whips are famous for harassing anyone who is thinking of voting against govt, and even keeping blackmail lists (which MP did naughty things the Whip could reveal). Whips are total ball-breakers, basically.

A lot of MPs were horrified at how they were being told to vote on fracking. Was perceived to break last Tory election manifesto. They'd lose their seat anyway, so unpopular with constituents.

To vote MPs literally line up at designated doors (yes/no), or 'lobbies'.

Whips came down heavy for this fracking vote. Chris Bryant (Labour MP) told Speaker to investigate because a Tory MP (Alex Stafford) was crying & got manhandled to go into a different voting group (Stafford denies he was manhandled btw). Rees Mogg was shouting at MPs in the lobbies. Loads of Tories voted against or abstained, including supposedly, Theresa May, Kwarteng and Truss herself. Nobody lost the Whip.

The Whips got furious at being asked to do the impossible and Quit on the spot. Truss ran down corridors after them begging them to stay.

It was an especially dramatic moment in a serious of incidents when Truss showed she had no authority over the Commons.

Before the PMs voted, conservative PMs were basically told that they had to vote the way that Truss told them (not in line with their own conscience/constituents interests etc) and anyone who didn't would basically be kicked out of the party. So essentially anyone voting against Truss's position on this was in effect saying they had no confidence in her. This was a particularly contentious thing to do because Truss' position on fracking was not in line with previous conservative manifesto promises. Things got heavy handed and even the people in charge of the voting didn't like what they were being asked to do. It sounds like Truss changed her mind about the consequences of voting against her and at the time of voting no one was really sure what the consequences were. So as well as showing that lots of her MPs disagreed with her and were willing to put their own positions on the line, the whole debacle made her look chaotic, lacking in support from her own party and out of touch.