It's frog in boiling water situation. For a long time the government was content with the money it could get from oil and mining, and many businesses were relatively safe. After the drop in oil prices and economic sanctions they started to get more creative, and the situation kept slowly worsening, until during this year there were multiple high profile cases like this.

Some say Igor didn't move because he's a patriot. Ironic, isn't it?

Well, I wouldn't necessarily call him a patriot or regime supporter or whatever (not a vocal one anyways), but he indeed did like to occasionally throw some stones towards non-systemic opposition, color revolutions supporters, or other likely-minded people. One example would be what he wrote 12.12.2015 (exactly 4 years prior to current incident) at http://sysoev.ru/ about Berezovskiy's alleged financial support of orange and tulip revolutions of 2004-5.

So in that respect it isn't that impressive that he stayed in Russia even when (mostly non-state) news became more and more disturbing. Probably even less so if you assume a line of reasoning that nobody would bother with relatively small foreign company built around open-source product, a company that's already sold to larger foreign company (conveniently forgetting about the price that F5 paid for that company).

(edit: s/american-registered/foreign/: Nginx Inc. was registered in British Virgin Islands)

He's being Matriotic. He lives in a Motherland, not a Fatherland.

It would indeed be ironic if he supports the current government. But in general patriot can also be someone who dislikes the crazy regime and doesn't want to give up his home without a fight.