Straight on paired non-flushy board facing huge river rr

[ShowMeAtlas]

This is my very first hand at the table. I presume there's really no other way to play the flop and turn.

Holdem No Limit - $0.2 BB

SB ($25.91)
BB ($40) [Hero]
UTG ($40.54)
MP ($11.57)
CO ($20.56)
Button ($8.30)

Hero is BB with 3, 6
Preflop: (6 players, $0.3)
UTG calls $0.20 and raises $0.20, MP calls $0.40, CO calls $0.40, Button calls $0.40, SB folds, Hero calls $0.20

Flop: 5, J, 5 (5 players, $2.1)
Hero checks, UTG checks, MP checks, CO checks, Button checks

Turn: 4 (5 players, $2.1)
Hero checks, UTG checks, MP bets $0.40, CO calls $0.40, Button folds, Hero calls $0.40, UTG folds

River: 2 (3 players, $3.3)
Hero bets $1.50, MP calls $1.50 and raises $9.27 and is All-In (oh dear), CO folds, Hero?

[Vi-Zer0Skill]

Looks like A-5 being a fool. Did you call?

[ShowMeAtlas]

Spot on! I dwelled and eventually decided on a call. A5 'twas! What led you to think that?

[Vi-Zer0Skill]

Lucky guess...?

My instinct was to assume that villian had A-5 because of how he played the flop. Granted that it may be wrong typically to assume the majority of micro limit players are sane, i imagine a PP would at least open on the flop to see where they are, especially a smaller one like 4-4 or 2-2 where a turn card only decreases the probability that they have the best hand. The weak turn lead also made me think of a slowplayed 5-x hand, and the overbet on the river was "a fool" thinking you didn't have the goods and hoping to induce a call with a medium strength hand. J-x hopefully would just call this river, but i guess A-J may be crazy enough to play this river this way. Very few hands play the river this way that you don't beat.

Oh yeah, a big pair may try something like this also, thinking that J-x will pay him off.