于是
yúshì
What just happened pushes your back, and you move
The picture The situation behind gives a shove, and the person, carried by that push, moves into the next action. 于是 is pushed into place by what came before; 然后 simply comes next in time.
Where the picture shows up in 于是
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Line busy, so straight to the house
电话一直占线，于是我直接去了他家。
diànhuà yìzhí zhànxiàn, yúshì wǒ zhíjiē qù le tā jiā
The line was busy the whole time, so I just went to his place.
the busy tone repeating, the phone pocketed, and feet turning into his street
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Rain, so the meeting moved
那天下大雨，于是会议改成了线上。
nà tiān xià dà yǔ, yúshì huìyì gǎi chéng le xiànshàng
It poured that day, so the meeting was moved online.
rain streaming down the window, the meeting room door pulled shut, a laptop opened instead
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Understood it, so hands went on
他听完就明白了，于是马上动手修。
tā tīng wán jiù míngbái le, yúshì mǎshàng dòngshǒu xiū
He understood as soon as he heard it, so he started fixing it right away.
a nod at the end of the explanation and a tool picked up in the same motion
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More guests, so more tables
客人越来越多，于是我们又加了两张桌子。
kèrén yuèláiyuè duō, yúshì wǒmen yòu jiā le liǎng zhāng zhuōzi
More and more guests came, so we put out two more tables.
the line at the door growing while a folding table is carried out of the back and opened
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Nobody could, so in the end (只好)
我们谁都不会做，于是只好上网查。
wǒmen shéi dōu bú huì zuò, yúshì zhǐhǎo shàngwǎng chá
None of us knew how, so we had to look it up online.
faces turning to each other blankly, then one laptop pulled over and a hand at the search box
All of it in one picture
于是 is a hand at your back. The line stays busy, so your feet end up at his door; the rain comes down, so the meeting moves into a screen. Understanding it and reaching straight for the tools, adding tables as the crowd grows, opening a search box because nobody knows how — all the same shove.