Interesting article @parietal. It doesn't really explain why Trump was spooked - he'd already said the road would be bumpy and there'd be some short term pain, but it would be worth it in the long run.
OP - Here's my view on why Trump was spooked by rising bond yields.... (simplified version):
Imagine you're a successful billionaire in the US - Mr Moose. You've created a hugely profitable global motorbike business, Moose Motorbikes.
All of your profits are in shares and share options, and various other tax advantaged schemes (because of course billionaires don't pay taxes).
Soon enough you want another challenge, so you decide to buy another company - say, a chain of motels. But you won't sell any shares in Moose Motorbikes because it would incur an eye-watering capital gains tax bill. How to raise the one billion needed to buy Moose Motels? You approach a bank to borrow the money you need at a very low interest (you're a billionaire so have a top credit rating), and offer to put up £1billion worth of shares in Moose Motorbikes as collateral - you don't have to sell them, but the bank knows they can claim them if you default. Now you can buy the chain of motels on credit, and any profits can be used to pay back the debt to the bank - a tax deductible expense (because of course billionaires don't pay taxes). Neat.
Alas disaster strikes - the US President imposes tariffs on the Asian country which supplies all of your raw materials and rare elements to build the motorbikes. This hugely increases manufacturing costs for Moose Motorbikes impacting profits. Worse still, other parts of the world are furious and try to boycott US products affecting your sales revenue. The share price of Moose Motorbikes sinks.
So, the bank sees the £1billion worth of shares you put up as collateral have dropped in value and it starts to get nervous - maybe they are only worth half a billion now. The bank is half a billion short of collateral on the loan. They give you a call and ask you to repay the half a billion short-fall back, so they will still be covered if you default.
Now Mr Moose has a dilemma - if you sell half a billion worth of shares in your own company when it's share price is already tumbling, it will crystallise your losses in the share price, incur a huge tax bill and signal that you no longer have faith in your own company. This might trigger a further sell off as investors take fright. How to raise the cash without selling shares? Well, you sell any bonds you've previously invested in.
But, imagine there are many billionaires and millionaires who operate the same business model of borrowing to raise capital to buy more assets like your motels. Their share prices are also falling and they are also receiving calls from their banks, and selling bonds to raise the money they need. This floods the bond market with too many bonds for sale so the price falls and the yield rises.
Now trying to sell bonds raises less money because the price has fallen, and you need to sell yet more bonds and soon you're in a downward spiral of falling prices and rising yields. (There is also a suspicion that the Asian country subject to tariffs is selling its own stock of US bonds to depress the price further to try to destabilise the US system).
If a lowly factory worker defaults on a bank loan, it's bad news for the worker - maybe he will go bankrupt - the bank absorbs the loss and the worker gets a very bad credit record.
But if several billionaires and millionaires can't raise sufficient cash to pay back the banks, then it's the banks that go bankrupt, and the whole system collapses.
As Trump said - people were getting a bit yippy....