Actually, Guaido's specific party boycotted the election. What you could loosely termed the 'right' is fragmented, and there's been some realy shenanigans going on with the supreme court booting out the leadership of parties on the right and replacing them with people who are more moderate and wanted to participate. Its all a bit murky, but then the opposition in Venezuela has been pretty bad at politics for some time.
From what I've read, the elections are unlikely to have any outright fraud on the day - however the actions of the supreme court and the electoral commission have been pretty poor over the last few years. Coupled with the general uselessnes of the opposition,brings the landslide results for Maduro's party.
However, turnout was terrible - 31%. My guess is that this reflects the cynicism of the general population rather than a mass movement allied with Guaido's call for a boycott.
What was interesting is that the bit of the left that broke away from Maduro's party (the PSUV) did not do very well. They accuse Maduro & the PSUV of moving away from the ideals of the revolution and becoming more statist and more right wing (the 'blockade law' being the straw that broke the camel's back).
Another interesting thing now will be what will happen to the Constituent National Assembly (the ANC). It was set up ostensibly by Maduro to rewrite the consitution and bring the country together in response to riots and unrest in 2017. However, its been operating as a parallent National Assembly (NA - different from the ANC, doo keep up
) since some dodgy supreme court decisions allowing that and has done nothing on developing a new constitution. The leader of the ANC is Diosado Cabello and I rather think he's got used to being an important national politican - with the NA now in Maduro's control, in theory the ANC can be disbanded. Expect some sweeties to be thrown Disoado's way or he'll start causing trouble!