But just claiming a similar name which is owned by other entity makes no sense as they can just buy it by offering a good price to the current owner if they want to protect there branding this much.
Yes a lot of big corporations just buy it outright without filing any lawsuits that's if the opposing business accepted to be bought out, blockchain.io might have refused to sell and rebrand their business but its most likely that blockchain.com is going to this route because they are confident on winning the case and the biggest benefit from that is they will officially have a legal claim on the word "Blockchain" itself, a very risky move but it will payoff if given a positive result. And yeah let us not forget that Bitcoin is a
trademarked name already by some London-based company.