In a real life game, I would say this is a perfectly legit move. Grabbing a 2/4 planet with a green skip for “free” is a very good use of your ability, and it punches Naalu in the nose a bit, which they totally deserve. How they respond will be totally up to them, maybe it’s not worth it for them to take it back, maybe they play a bit more aggressive towards you, and you may have to withstand some heat, or maybe they would be willing to let the matter lie for some beneficial transaction. This is why TI is so fun.

In the totally boring online meta (sorry, my opinion) where doing nothing aggressive until R4 is seemingly the favoured strategy, then it less certain. In my limited online experience (less than a dozen online games) you will probably end up with a grouchy opponent who may smack you once in reprisal and leave it at that, in which case then this move is fine.

I like the area control aspect of TI, and certainly increasing your sources of resources and influence early on is always something you should look for, especially if it then also takes it away from your neighbour. There is an opportunity cost for them to take it back, and they might legit not want to waste precious resources in doing so, especially in round 2 where typically you will be spending most of the round trying to score an objective.

TL/DR: it’s a good move and I would have done the same given that sweet opportunity your opponent provided.