Midlothian was very closely contested between the SNP and Labour across the previous two elections, so although modest, this is the largest SNP vote lead yet. A gain of two seats to 8 also gave them a seat advantage over Labour too, who were unchanged on 7. This came from a big drop in Conservative support, with their two losses leaving them with 3 seats.
As they had in 2017, the Greens suffered from the fact Midlothian is entirely three-member wards, so despite a solid vote share increase they still didn’t elect a councillor. Lib Dems did increase their share too, but still on the low end for them.
After the election, an SNP minority administration was formed.
Modern Midlothian is very much a shadow of its former self. It had already lost the historic centre at Edinburgh before the advent of true local government, and then in the 70’s was further truncated with the loss of everything west of the Pentlands, Musselburgh, and the area around Heriot. The area remaining was largely defined by mining for much of the 20th Century, though perhaps not to the same degree as West Lothian.
That naturally led to Labour consistently winning Westminster seats covering the area right up until the SNP’s 2015 landslide. They were strong enough here that Midlothian was one of their 2017 gains, brief though they proved. In the Scottish Parliament the SNP relieved Labour of their Midlothian seat in 2011, though due to boundary changes they also could be considered to have displaced a Lib Dem that had held a mostly Borders seat with a sliver of Midlothian in it.
Apart from a brief spell where Labour fell one short of a majority after the 1977 election due to an SNP surge, they barely had a handful of opposition councillors for decades. That was mostly in the form of Conservatives during the District Council period, followed by the SNP then Lib Dems after the unitary councils were created in the 90’s.