Any expert can explain the reason behind those huge pump and dumped of BTC?
Not an expert by any means but I will put my views on the topic because I feel like I know something about the pump and dump that is going on for years.
First of all, the BTC market is volatile because trading happens without any data, I mean in the standard stocks market it is easy to estimate how much a particular share or asset was sold and bought but it's near impossible to calculate that in the crypto market hence the volatility.
Now, coming back to the point who causes these pumps and dumps? It's most of the time the whales like you said Elon can do it, that's true. Why they do it? Obviously to eat the capital of a nervous small trader and those who are trading with leverage or futures.
One thing you didn't ask but I feel I should answer is, how we can avoid being affected by these? By avoiding futures trading and ensuring not to panic when the market goes down. Just read about the GameStop share and how people killed those who do short selling because they just hold their shares and at a certain point, whales who did short-selling lost gigantic amount of money.