The deal is subject to shareholder approval. I think based on that approval, you'll be able to estimate how right or wrong you are about lawsuits had the board rejected the offer.
RHT is $20 billion in market cap as of Friday, and the offer is $34 billion.
The Red Hat board were offered a massive premium on an already generously-priced stock. If they hadn't sold there probably would've been lawsuits left and right.