Sorry really not sure what you're saying in your second statement? And apologies if I've wrongly interpreted your first sentence but it looks facetious. If you neither know or care who Paul Dianno was just move along and let those of us who think he contributed something musically to our lives pay tribute.
Paul's problem was 'playing' too hard away from the stage with the usual rock star attraction to booze and substances. His performances on stage started to suffer and he couldn't cope with the all ready punishing touring schedule. Bruce not only had a much wider vocal range but as you suggest knows how to work a crowd.
I used to be into Maiden back in the 90's and I think Killers is their best album
You do realise that that was not their own song but a cover version they felt pressured into releasing by their then publishing company Zomba. They've always denounced it's release as a mistake.
That's a pretty fair assessment. Fame and it's pressures came too quickly and early for Paul. Steve Harris and their manager Rod Smallwood ( lives in Hove
) were never going to let Paul's frailties derail the Maiden promotional juggernaut back then which was based on relentless touring.
I’m aware it was a cover.
I suspect ‘tap chose to resemble them to be fair… which is probably enough to suggest that Maiden we’re good enough to parody whilst producing awesome piss takes like Stone’enge …
which inspired me to try and write a song called unholy nuns… 
I never got beyond the opening line:If anything the Spinal Tap charge is perhaps more valid from the mid 80's when Paul had left and the stage sets became more spectacular and elaborate. However, I'd always argue that Maiden's approach has always been greatly tongue in cheek with few ' collapsing Stone Henge' moments. The whole Eddie mascot and the Maiden font has proven to be a brilliant marketing ploy and exercise in branding. People might not like them but the world has heard of them!
Yeah, I’d agree with that.
My only criticism in recent years is they've over done it with the too many prog rock like tracks dominating their albums. Too many 6 minute plus songs isn't always easily digestible. You need light and shade with a mix of the sprawling story telling epics and the 3 minute belters.