The key part here is "for 2022 and 2023"
If Aloiai wants to go for more money once his contract is up, then that's his business
Apparently he is on $350,000 for 2021. So an immediate step up to $500-$600K at Manly is a pretty good motivator (let alone the bigger upgrade for 22 and 23).
To me this all stems back to the bigger issue of paying overs for dud players and with those values being widely reported, other team members are going to compare...
Packer ~$3mil over 4 years,
Reynolds ~$3mil over 4 years (both barely playing first grade),
Moses Mbye north of $3mil over 4 years (selected, but also barely first grade quality),
Ben Matulino signed for ~$800K per season (medically retired for this year).
Josh Aloiai is probably sitting there thinking, those guys don't offer the club that much, but get paid like royalty.
Meanwhile, I'm the cornerstone of this pack and the club is only prepared to offer me less than half what those guys are being gifted - screw this, I'm outta here!
They've basically offered him about the same contract as Chris McQueen got for 3 years (and played the equivalent of about 6 games over that period).
Bad signings are a double-ended killer - you tie up your salary cap with junk for four years, but I think it also dis-engages players who know they're worth more (with their agents telling them they're worth more) and so you lose your good talent too.