I've had two challenging 4yos and they were both easy at 2, a bit more challenging at 3, but 4 was the absolute killer. My current 2yo is easy again IMO so I'm sure I've got it all to come again 😨
I have wondered if it's parenting style related - how would you all describe your parenting style? I tend towards being quite "gentle parenting" which for me was how to talk so kids will listen / control the environment rather than the child / distract, validate and redirect rather than blame/shame/expect compliance etc. And I think this leads to three things: -
First, the twos are much easier because you're not constantly giving them commands, and then waiting for them to comply (or not) and reacting positively/negatively accordingly. This doesn't REALLY work for 2yos, even though it's the received one size fits all parenting approach that's supposed to work for all children, which is why age 2 has the reputation for being terrible. So it neatly avoids all that conflict with a 2yo because you're not expecting them to be compliant in the first place, and you'll tend to have a wonderful time at two. However, by the time they get to four, most children who have been parented in the more "standard" way ARE getting the hang of it and are basically compliant most of the time. So if you've not been "training" that, they will totally stand out against other children their age. You're basically butting up against the terrible twos anyway, just two years later.
Secondly, you can be lulled into a false sense of confidence in your own ability to set boundaries, especially if you were attracted to this kind of parenting style because you're conflict-avoidant. 2 year olds are very easily distracted, redirected, and comforted, and so you can think "Well, I got them to stop doing that thing - I held the boundary!" The same tricks don't work so well for 3 and 4 year olds. If you've got used to "holding boundaries" in a very stretchy, roundabout way ie letting child think that they have won, outsmarting them, or just distracting them away from their frustration, you're likely to run into issues at the later end of three coming into four, because children start to develop more sophisticated thinking processes and they will dig their heels in harder and fight harder and be less easily persuaded, and you'll then frequently find that you run out of rope, patience, tricks etc before they do and then you don't know what to do because in reality you haven't actually got solid boundary holding skills.
Lastly, I think you can fall into a trap where, by trying to avoid any notion of shame or blame, and sometimes when trying to protect children from experiencing difficult emotions, or prevent tantrums, you end up giving children control without responsibility, without holding them accountable so to speak, and this can end up with the "little dictator" who thinks that the world revolves around them and why wouldn't it, because it always has and nobody ever demands anything back from them, they expect everything to be a transaction or negotiation, of which they are ultimately in control.
I don't have great solutions for any of these BTW but I do think understanding the problem is one step towards solving it.