The best way of seeing this is to understand that The Lion King isn't actually a faithful retelling of actual events, but a Mufasa dynasty-sanctioned royal chronicle that completely distorts history. If you take this into heart and read (watch?) between the lines, these things become clear:

1. Mufasa was an unpopular despot. Notice how in the retelling of his death by wildebeest, there was never a sense that the wildebeests tried to cushion his fall, tried to help Mufasa, or even expressed regret for trampling their king. This is because Mufasa was actually a despot who was killed by a mob of wildebeest peasants tired of his reign.

2. Scar being queer-coded is just the so-called Mufasa royal family being complete homophobic pieces of shit. It also buried the fact that Scar had sire and even appointed an heir when Simba was about to retake the throne. What The Lion King didn't tell you was the decade-long purge where Simba hunted down and exterminated Scar's entire extended family, including torturing and beheading Scar's son and sticking the head onto a wooden spike as an example.

3. The Lion King trafficked typical anti-hyenaism despite hyenas not actually being supporters of Scar. Being relatively lukewarm towards Scar's reign, the deeply rooted anti-hyenaism of Pride Rock meant that any imagined retelling of Scar's reign will place them in front as Scar's loyal myrmidons. The publishing of The Lion King led to a massive pogrom, where thousands of hyenas were killed by an anti-hyenaist pro-Mufasa mob.

4. Scar actually had support among various members of the lion aristocracy. This was due in part to Mufasa's terrible management of Pride Rock and Simba's hedonistic lifestyle and general incompetence. The battle in which Simba retook the throne had lions on both sides of the battle. In fact, the battle was largely lion vs lion, not lion vs hyena as depicted in the royally sanctioned chronicle. Scar's fate was sealed when he decided to limit the feudal privileges of the lion aristocracy, which meant he was outnumbered in the confrontation.

5. Simba eating the bugs was just ridiculous inversion of the real Simba, a massive carnivore who hunted his subjects for sport, callously leaving their dead bodies to rot in the hot sun as his so-called "royal right."

6. The crop failure solely attributed to Scar's reign is just typical Mufasa propaganda to signal that Scar lost the Mandate of the Circle of Life. In fact, the drought began during Mufasa's reign and was greatly exacerbated by Simba's wanton lifestyle. The drought continued during Simba's reign, only ending many moons later. Initially, the drought was used as an excuse to conduct anti-hyena pogroms during Mufasa's reign before being weaponized to denigrate Scar.

As for a true evaluation of Scar's reign, it was largely a mediocre one. He was less ruthless than Mufasa and less hedonistic than Simba, but Scar never was able to break the stranglehold the lion aristocracy had over the feudal subjects of Pride Rock. Scar understood that the herbivore peasantry was suffering and a source of instability, but he realized too late that the contradiction between the herbivore peasantry and the carnivore aristocracy was an antagonistic one.