Reasons I see:

a) the generation that grew up watching LTT is now at age where they don't watch as much YT as they did before b) increasing amount of things happen which put viewers off c) consumer technology peaked and is now "boring" d) new generations don't have as much interest in technology altogether

Let's explain:

a + c) people watching LTT years ago were living in an exiting tech era where it boomed and you had mayor leaps in tech basically on a yearly basis. Moving from floppy disks to CD's to USB sticks. CRT to LCD displays. 16-bit to 32-bit color. Solitare and Minesweeper to Call of Duty 4 and Need for Speed. Symbian and Blackberry to Android and iOS. Tons of manufacturers, tons of competition, tons of new and exctiting stuff.

Let's observe the state today: iPhone looks the same for the past half decade. Android is basically just Google and Samsung. Storage is now all in cloud. New games are recycled and upscaled old games. Every new generation of hardware is same thing just 10% better/faster. New OS releases are just refinements without new features. Most changes are done just for the sake of change. Existing hardware can basically be enough for 5+ years. What is LTT realistically supposed to talk about that is interesting? There is simply no more interesting tech.

This ties in into d) - tech peaked, new generations "just use it as it is", there is no need to tinker with it, prebuilt PC's are more than fine for years to come. Since AI the IT job landscape seems to be in decline, both in demand and in pay. People do other stuff now that is more lucrative.

LTT is dependent on stuff happening so that they can make videos about it. But, stuff kinda just isn't happening. Or the stuff that happens is just not noteworthy news anymore.