Are Banks injecting unlimited FIAT to control limited cryptocurrencies
![Huh](https://bitcointalk.org/Smileys/default/huh.gif)
haha, if they attack like this we will soon replace their system with bitcoin
![Cheesy](https://bitcointalk.org/Smileys/default/cheesy.gif)
but no, you are overthinking things. bitcoin is growing because as you said Japan legalized it and that led to a massive increase in Japanese volume rushing to buy bitcoin and the rest of the world has been reacting to the news too. they are also buying bitcoin and a couple of other countries are taking the same legalizing path.
and as for altcoins, this happens almost every year when they get pumped and take a lot of money from bitcoin invesstors not anybody from outside, and go up a lot into bubbles. and then they pop and die slowly until next pump round.