Tarpits can show up even in simple domains.
Some domains are inherently complex; there is no way to make progress without powering through a tarpit.
But some domains aren't that complex, but can become tarpits.
These emergent tarpits show up when you thrash.
The more you do it the more you get stuck in the problem.
There's always a rabbithole to get sucked deeper into.
If the path through is constantly changing, it can make it harder to make progress.
The longer you're stuck in the tarpit, the more stuck you become.
If you're searching for the perfect path through the tarpit, you might constantly second guess the current plan, and thrash to another non-perfect answer, getting stuck more in the tarpit trying to figure out the best way out.
Often what you need is just a good enough path to traverse the tarpit and get out as quickly as possible.
If you're impatient about getting out of the tarpit, you make everyone else more nervous, which makes them get more stuck in the tarpit.