Fair point. The demonisation of Corbyn certainly played a part, but I feel you are ignoring the impact of the simplistic 'get brexit done' message. Boris had literally nothing else to commend him. His govt had overseen 10 years of austerity, and his personal flaws were all well known. It seems that the GE result, or that graph inaccurately reflect public opinion on Brexit - in the absence of proof to the contrary it must be the graph that's bollocks. The public had a clear centrist remain choice in the lib dems if ther really wanted remain/revoke and labour /corbyn were too left wing.
The EU referendum, EU elections, and GE all gave the UK public another opportunity to change the direction of travel if they wished, but actual votes which carry more weight than polling consistently reflected the wish to leave the EU.