I guess Nintendo is very worried about the transition from Switch 1 to 2, guessing it is the first time they're doing something that isn't an entirely new console idea (apart from the handhelds, of course, but even then they differed a lot). Nintendo Switch's launch lineup was not the most incredible thing ever either, it had BoTW, some other fun games like Snipperclips and 1-2 Switch as a showcase to the joy-cons co-op kind of thing. Initially, the Switch's gimmick was what gave it the most sales, software quantity and quality grew over time, but did not release with a lot on it initially.
They might want to be a bit more aggressive on the launch titles this time to smooth out this transition between generations and give the new Switch something like the Xbox One -> Series or PS4 -> PS5 sort of thing. Makes total sense to me at least, although it's bumming they will delay the release for that. But if that gives better momentum for their launch and better games for me to play, i'm fine with all delays.
EDIT: Plus, i don't see why some people tend to believe this is a problem with hardware-side of things. Things like chipsets and SoCs to be used on systems like this are planned and tested for years upfront, software is a harder deal because deadlines are tighter and readiness of those are volatile. I'm sure the chipset is just fine, most likely they will use the additional time to build better stock for the release too.