I think India may have acted as a catalyst to improve the relationship between the Biden and MBS. Both personality are not very friendly towards each-other, especially after the J Khashoggi murder. Biden's pressure on the prince(because of them being democrats &muH deMoCracy FreDom equality voterbase) had deteriorated their personal relation-ship and they were not comfortable around each-other. While USA's reluctance to fully provide SA's security against the Iranian aggression. So, India may have provided a window for reconcialliation.
India had been actively supporting Russia by asking USA to not put too much pressure on Russia for the Ukraine war. India is doing so that Russia do not go fully into the China's camp and have been vouching for them!!
The railway project is fully funded by GCC countries. Its a $250 billion project wanting to connect all the Gulf countries and the project is called Gulf Railway!! Israel is also on the talks for the same railway!! India does not have to pay any development fee!!