Hint: It's about protection of the religion (today those who have disbelieved have despaired about your religion....).
But if you wish to spoon fed. God takes us into a time and moment when he perfected the religion. How did this happen?
Another hint: We are reminded of the children of Israel being risen twelve Navigators and Captians of the ship of salvation which by the name of God it's sailing and anchoring, through a covenant as well, but the hard hearts of children Israel broke the covenant, didn't help those Messengers, and dishonored them. They did this first by twisting words way out of their place.
Another hint: Musa and Haroun separated from their people because they could no longer "control them" and Musa didn't have authority over anyone but himself and his brother, and so while God completed the religion, he did his part, things can still go wrong.
Another hint: The books of the past were meant to be judged by but Quran still warns as the people entrusted these books went astray, not to take them as "Awliya" and in this context it means as authorities over these books and religion. Yet we see Mohammad (s) is disputed by hypocrites on grounds of some of these people of the book out of love for them and we see this not only in this Surah but others, that they would look to see what Christian and Jewish scholars said about Mohammad (s) in their books and remember that Yathrib were filled with "people of the book" who were waiting for Mohammad (s) and hence invited him in the first place to rule them, yet many didn't believe and lied about Mohammad (s) or didn't believe but pretended to. In this context and in warning believers not turn on their backs, it says "Your Wali (Authority) is only God, the Messenger, and those who secured, those who keep up Salah and give Zakat while bowing", and this was Ali (a) per hadiths when giving a ring to a poor person asking for charity while everyone was praying, it was only Ali (a) who showed his ring and gave it to him. And it's plural, and so he represents the Imams.
Another hint: "Convey what you have been revealed from your Lord...." is revealed for Imam Ali (a) at Ghadir and it doesn't make sense to say convey Quran if you didn't convey Quran, you didn't convey Quran, that makes no sense.
And the Surah itself speaks of start of Bani-Israel and end of them as far the Captains of the ship of salvation goes they had to steer them upon the right direction.
Of course, those who "disbelieve" know they can't put out God's light about Ali (a) and ahlulbayt (a) in Quran. That Welayat of chosen ones will be there in the Sunnah has Ghadeer event wrote that in history without ambiguity.
As the Sunnah is meant to safeguard the interpretation, this was a way of Mohammad (s) of keeping the religion alive forever.
Now we know there is "divisions", but Allah (swt) gave a way to unity. The umma failed, same way Bani-Israel failed, to keep to Twelve Navigators (a) after Musa (a) for them starting with Haroun (a) and ending with Isa (a).
There is still a way to unity. And the words stand as a proof and the truth is clear.
Research Ghadir event.
The last verses revealed were put in Meccan Surahs, that is, early Surahs, and the last two verses was revealed when someone said about Welayat Ali (a) "if this is the truth then bring upon me punishment". The last two verses "An asker asked about a punishment bound to come, for the disbelievers there is no one who can prevent it". Of course, he was killed by a rock dropping on him from the sky, but the over all context of it, is a warning about the Mahdi (a).
And this was put into an overall Meccan Surah, and so we see according to the truth, some Meccan verses find their way to overall Medina Surahs and some Medina verses find themselves in Meccan Surahs.
And Surah Maeda contextualizes the story of Abel and Cain, in that, Qabel (Cain) killed Abel because God accepted from Abel but not Cain.
And this is the motive of Shiites being oppressed. It's pure hate and envy. Because we hold you must accept Welayat of Imams (a) to be a believer and accepted by God, we faced severe oppression.
And you see also "anti-judgmental" people hate believers because we believe in hell for those who don't accept the clear proofs of God's religion and don't submit sincerely to God.