“He knew that his enemies . . . would never give him credit for saving Israel. He did it anyway.”
That line says it all.
When he got ‘the call’ from Israel for help - he said his mother told him - when he was young - you are here to help Israel - do whatever you can to help them. And he did.
As a mater of fact, before the war began, Russia had been supplying Egypt with a steady build up of their latest weapons. So to put it in perspective, Nixon was only doing what Russia had been doing; supplying Israel. Politically Nixon would hold the high ground if Russia had sent troops. The Russians knew this.