My grandfather left five moving cartons of diaries written by typewriter, every single day of his adult life documented, an achievement, to be sure. When he passed away he left them to my mother to be scanned, transcribed and moved online, something that weighed her down for the last 15 years of her life.
When he died there was no way of transcribing them automatically (there still isn't really). The boxes stood in my mothers already cramped attic for 13 years, then she got cancer, and she felt a need to finish up things, so she got a scanner and started just scanning.
When my mother died she had scanned about a thousand pages, not transcribed, not anything.
The text in the diaries were fun at times, sometimes depressing, seeing how little he cared about my mother and his family was crushing.
My brother wanted to continue the scanning but I told him that I wanted to throw the diaries away. He kept half a year of writing around his birth (there's at least a sentence) and my uncle did the same, then we just watched it all burn (not literally, we threw it away at the recycling centre).
Not everything needs to be preserved. I'm happy some parts is preserved. I'm happy that those diaries are ash.
Friendly spelling correction. Diaries, not dairies. Dairies are where one produces dairy products.
And I'm sorry your mom experienced that weight towards the end of her life. That sounds like a significant thing to grapple with, especially considering some of the not so pleasant content mentioned.
I understand there may be an emotional desire to get rid of something unpleasant, but some descendants e.g. 5 generations down the line may feel very differently about this. Given how easy scanning is these days (there are literally companies that will do it for you if you send them a box), and given how good the technology for sifting through mountains of text is becoming, and given that it's literally irreplaceable text, I can't imagine doing this to family records that one of my ancestors specifically wanted to be preserved. Not criticizing your personal decision of course, but just offering a different perspective, i.e. for me it would be unimaginable to do this.