flying a $1k toy into high temperatures is just an attempt at a stock fotog to get some footage and some publicity. science was nowhere near on the agenda. the guy runs a stock photo company specializing in aerials.
I'm sure you can use a better camera, but I think in 2021, you definitely use unmanned drones.
And then, safe just means nobody gets hurt. The volcano will eat some instrumentation anyway at some point, probably. They often do. Plus, the sulfuric acid plume emissions will damage your gear if you get caught in it.
The risks associated with being 5km away piloting a drone and in a helicopter full of people overhead is radically different.
I mean, I wouldn't have wanted to be only 5km away from Mt St Helens when It blew its top ~40 years ago, but that one had spent 6 weeks giving off 4 and 5 magnitude earthquake warnings...
I think there's be a huge range of volcanos where it'd be risky to overfly in a helicopter risking human life, but where it'd be perfectly safe and sensible to fly drones for fun/curiosity/commercial-stock-footage/education/some-possible-eventual-science-benefit. I mean the major reason _not_ to overfly sites with drones are entirely absent, there's nobody and nothing valuable to hit and nothing for a drone battery to set fire to if you crash one on a lava field...
Not sure if we went directly over the crater, but either way, that's an eruption that has gone on for decades, and behaves in known ways.
The Iceland eruption is a few days fresh.
(Especially Hawaiian and the Icelandic volcanoes are usually not that bad (unless the eruption is below a glacier, that's quite explosive).)
So, the $1k toy is actually being trialed around the world, just with more complex instrumentation. You can get closer without risking anyone, and you can make much more frequent measurements since it's so much cheaper. The biggest problem is the wind and turbulence (since volcanoes are mountains with a heat source, and almost nobody in the field is an experienced drone pilot).