No, he couldn't, the widely discussed breakup fee in the contract was a payment if the merger could not be completed for specific reasons outside of Musk’s control.
It wasn’t a choice Musk was able to opt into.
OTOH, IIRC, he technically wasn't forced to because he completed the transaction voluntarily during a pause in the court proceedings after it was widely viewed as clear that he would lose and be forced to complete the deal.
It was looking like he would lose and the courts would force the sale, but the case was settled without a judgement by Elon fulfilling his initial obligation of buying the website.