If he must buy TWTR at his advertised price with his own cash, he must liquidate way more TSLA - about 44bln$ worth, as far as I remember. He actually will have to liquidate way more, because liquidation is a taxation event, and he'll have to pay a significant percentage of his gains to the US government. I don't know how much he needs to liquidate, but I'd guess it's more like 60-70bln$.

Liquidating such an amount of TSLA in a short time will not happen without significant reduction of TSLA stock price. Musk will probably still be a multi-billionaire afterwards, but it would cost him several billions on the TSLA and TWTR front, because he would have overpaid for TWTR, TSLA share price would have tanked and he would have paid billions in taxes.

The whole point is that he secured funding from third parties for the Twitter deal. He was never buying it alone.

He said he is liquidating because that funding may fall through. He has a different idea of what funding secured means.

He will most likely use loans with the stocks as collateral.